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heading">¶</a></h1>227<p><strong>Source code:</strong> <a class="extlink-source reference external" href="https://github.com/python/cpython/tree/main/Lib/socketserver.py">Lib/socketserver.py</a></p>228<hr class="docutils" />229<p>The <code class="xref py py-mod docutils literal notranslate"><span class="pre">socketserver</span></code> module simplifies the task of writing network servers.</p>230<div class="availability docutils container">231<p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: not WASI.</p>232<p>This module does not work or is not available on WebAssembly. See233<a class="reference internal" href="intro.html#wasm-availability"><span class="std std-ref">WebAssembly platforms</span></a> for more information.</p>234</div>235<p>There are four basic concrete server classes:</p>236<dl class="py class">237<dt class="sig sig-object py" id="socketserver.TCPServer">238<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">TCPServer</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">server_address</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">RequestHandlerClass</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">bind_and_activate</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">True</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.TCPServer" title="Link to this definition">¶</a></dt>239<dd><p>This uses the internet TCP protocol, which provides for240continuous streams of data between the client and server.241If <em>bind_and_activate</em> is true, the constructor automatically attempts to242invoke <a class="reference internal" href="#socketserver.BaseServer.server_bind" title="socketserver.BaseServer.server_bind"><code class="xref py py-meth docutils literal notranslate"><span class="pre">server_bind()</span></code></a> and243<a class="reference internal" href="#socketserver.BaseServer.server_activate" title="socketserver.BaseServer.server_activate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">server_activate()</span></code></a>.  The other parameters are passed to244the <a class="reference internal" href="#socketserver.BaseServer" title="socketserver.BaseServer"><code class="xref py py-class docutils literal notranslate"><span class="pre">BaseServer</span></code></a> base class.</p>245<div class="versionchanged">246<p><span class="versionmodified changed">Changed in version 3.15: </span>The default queue size is now <code class="docutils literal notranslate"><span class="pre">socket.SOMAXCONN</span></code> for <a class="reference internal" href="#socketserver.TCPServer" title="socketserver.TCPServer"><code class="xref py py-class docutils literal notranslate"><span class="pre">socketserver.TCPServer</span></code></a>.</p>247</div>248</dd></dl>249 250<dl class="py class">251<dt class="sig sig-object py" id="socketserver.UDPServer">252<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">UDPServer</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">server_address</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">RequestHandlerClass</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">bind_and_activate</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">True</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.UDPServer" title="Link to this definition">¶</a></dt>253<dd><p>This uses datagrams, which are discrete packets of information that may254arrive out of order or be lost while in transit.  The parameters are255the same as for <a class="reference internal" href="#socketserver.TCPServer" title="socketserver.TCPServer"><code class="xref py py-class docutils literal notranslate"><span class="pre">TCPServer</span></code></a>.</p>256</dd></dl>257 258<dl class="py class">259<dt class="sig sig-object py" id="socketserver.UnixStreamServer">260<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">UnixStreamServer</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">server_address</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">RequestHandlerClass</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">bind_and_activate</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">True</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.UnixStreamServer" title="Link to this definition">¶</a></dt>261<dt class="sig sig-object py" id="socketserver.UnixDatagramServer">262<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">UnixDatagramServer</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">server_address</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">RequestHandlerClass</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">bind_and_activate</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">True</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.UnixDatagramServer" title="Link to this definition">¶</a></dt>263<dd><p>These more infrequently used classes are similar to the TCP and264UDP classes, but use Unix domain sockets; they’re not available on265non-Unix platforms.  The parameters are the same as for266<a class="reference internal" href="#socketserver.TCPServer" title="socketserver.TCPServer"><code class="xref py py-class docutils literal notranslate"><span class="pre">TCPServer</span></code></a>.</p>267</dd></dl>268 269<p>These four classes process requests <em class="dfn">synchronously</em>; each request must be270completed before the next request can be started.  This isn’t suitable if each271request takes a long time to complete, because it requires a lot of computation,272or because it returns a lot of data which the client is slow to process.  The273solution is to create a separate process or thread to handle each request; the274<a class="reference internal" href="#socketserver.ForkingMixIn" title="socketserver.ForkingMixIn"><code class="xref py py-class docutils literal notranslate"><span class="pre">ForkingMixIn</span></code></a> and <a class="reference internal" href="#socketserver.ThreadingMixIn" title="socketserver.ThreadingMixIn"><code class="xref py py-class docutils literal notranslate"><span class="pre">ThreadingMixIn</span></code></a> mix-in classes can be used to275support asynchronous behaviour.</p>276<p>Creating a server requires several steps.  First, you must create a request277handler class by subclassing the <a class="reference internal" href="#socketserver.BaseRequestHandler" title="socketserver.BaseRequestHandler"><code class="xref py py-class docutils literal notranslate"><span class="pre">BaseRequestHandler</span></code></a> class and278overriding its <a class="reference internal" href="#socketserver.BaseRequestHandler.handle" title="socketserver.BaseRequestHandler.handle"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle()</span></code></a> method;279this method will process incoming280requests.  Second, you must instantiate one of the server classes, passing it281the server’s address and the request handler class. It is recommended to use282the server in a <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement. Then call the283<a class="reference internal" href="#socketserver.BaseServer.handle_request" title="socketserver.BaseServer.handle_request"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle_request()</span></code></a> or284<a class="reference internal" href="#socketserver.BaseServer.serve_forever" title="socketserver.BaseServer.serve_forever"><code class="xref py py-meth docutils literal notranslate"><span class="pre">serve_forever()</span></code></a> method of the server object to285process one or many requests.  Finally, call <a class="reference internal" href="#socketserver.BaseServer.server_close" title="socketserver.BaseServer.server_close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">server_close()</span></code></a>286to close the socket (unless you used a <code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code> statement).</p>287<p>When inheriting from <a class="reference internal" href="#socketserver.ThreadingMixIn" title="socketserver.ThreadingMixIn"><code class="xref py py-class docutils literal notranslate"><span class="pre">ThreadingMixIn</span></code></a> for threaded connection behavior,288you should explicitly declare how you want your threads to behave on an abrupt289shutdown.  The <code class="xref py py-class docutils literal notranslate"><span class="pre">ThreadingMixIn</span></code> class defines an attribute290<em>daemon_threads</em>, which indicates whether or not the server should wait for291thread termination.  You should set the flag explicitly if you would like292threads to behave autonomously; the default is <a class="reference internal" href="constants.html#False" title="False"><code class="xref py py-const docutils literal notranslate"><span class="pre">False</span></code></a>, meaning that293Python will not exit until all threads created by <code class="xref py py-class docutils literal notranslate"><span class="pre">ThreadingMixIn</span></code> have294exited.</p>295<p>Server classes have the same external methods and attributes, no matter what296network protocol they use.</p>297<section id="server-creation-notes">298<h2>Server Creation Notes<a class="headerlink" href="#server-creation-notes" title="Link to this heading">¶</a></h2>299<p>There are five classes in an inheritance diagram, four of which represent300synchronous servers of four types:</p>301<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="o">+------------+</span>302<span class="o">|</span> <span class="n">BaseServer</span> <span class="o">|</span>303<span class="o">+------------+</span>304      <span class="o">|</span>305      <span class="n">v</span>306<span class="o">+-----------+</span>        <span class="o">+------------------+</span>307<span class="o">|</span> <span class="n">TCPServer</span> <span class="o">|-------&gt;|</span> <span class="n">UnixStreamServer</span> <span class="o">|</span>308<span class="o">+-----------+</span>        <span class="o">+------------------+</span>309      <span class="o">|</span>310      <span class="n">v</span>311<span class="o">+-----------+</span>        <span class="o">+--------------------+</span>312<span class="o">|</span> <span class="n">UDPServer</span> <span class="o">|-------&gt;|</span> <span class="n">UnixDatagramServer</span> <span class="o">|</span>313<span class="o">+-----------+</span>        <span class="o">+--------------------+</span>314</pre></div>315</div>316<p>Note that <a class="reference internal" href="#socketserver.UnixDatagramServer" title="socketserver.UnixDatagramServer"><code class="xref py py-class docutils literal notranslate"><span class="pre">UnixDatagramServer</span></code></a> derives from <a class="reference internal" href="#socketserver.UDPServer" title="socketserver.UDPServer"><code class="xref py py-class docutils literal notranslate"><span class="pre">UDPServer</span></code></a>, not from317<a class="reference internal" href="#socketserver.UnixStreamServer" title="socketserver.UnixStreamServer"><code class="xref py py-class docutils literal notranslate"><span class="pre">UnixStreamServer</span></code></a> — the only difference between an IP and a Unix318server is the address family.</p>319<dl class="py class">320<dt class="sig sig-object py" id="socketserver.ForkingMixIn">321<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">ForkingMixIn</span></span><a class="headerlink" href="#socketserver.ForkingMixIn" title="Link to this definition">¶</a></dt>322<dt class="sig sig-object py" id="socketserver.ThreadingMixIn">323<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">ThreadingMixIn</span></span><a class="headerlink" href="#socketserver.ThreadingMixIn" title="Link to this definition">¶</a></dt>324<dd><p>Forking and threading versions of each type of server can be created325using these mix-in classes.  For instance, <a class="reference internal" href="#socketserver.ThreadingUDPServer" title="socketserver.ThreadingUDPServer"><code class="xref py py-class docutils literal notranslate"><span class="pre">ThreadingUDPServer</span></code></a>326is created as follows:</p>327<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">class</span><span class="w"> </span><span class="nc">ThreadingUDPServer</span><span class="p">(</span><span class="n">ThreadingMixIn</span><span class="p">,</span> <span class="n">UDPServer</span><span class="p">):</span>328    <span class="k">pass</span>329</pre></div>330</div>331<p>The mix-in class comes first, since it overrides a method defined in332<a class="reference internal" href="#socketserver.UDPServer" title="socketserver.UDPServer"><code class="xref py py-class docutils literal notranslate"><span class="pre">UDPServer</span></code></a>.  Setting the various attributes also changes the333behavior of the underlying server mechanism.</p>334<p><code class="xref py py-class docutils literal notranslate"><span class="pre">ForkingMixIn</span></code> and the Forking classes mentioned below are335only available on POSIX platforms that support <a class="reference internal" href="os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal notranslate"><span class="pre">fork()</span></code></a>.</p>336<dl class="py attribute">337<dt class="sig sig-object py" id="socketserver.ThreadingMixIn.block_on_close">338<span class="sig-name descname"><span class="pre">block_on_close</span></span><a class="headerlink" href="#socketserver.ThreadingMixIn.block_on_close" title="Link to this definition">¶</a></dt>339<dd><p><a class="reference internal" href="#socketserver.BaseServer.server_close" title="socketserver.BaseServer.server_close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ForkingMixIn.server_close</span></code></a>340waits until all child processes complete, except if341<a class="reference internal" href="#socketserver.ThreadingMixIn.block_on_close" title="socketserver.ThreadingMixIn.block_on_close"><code class="xref py py-attr docutils literal notranslate"><span class="pre">block_on_close</span></code></a> attribute is <code class="docutils literal notranslate"><span class="pre">False</span></code>.</p>342<p><a class="reference internal" href="#socketserver.BaseServer.server_close" title="socketserver.BaseServer.server_close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ThreadingMixIn.server_close</span></code></a>343waits until all non-daemon threads complete, except if344<a class="reference internal" href="#socketserver.ThreadingMixIn.block_on_close" title="socketserver.ThreadingMixIn.block_on_close"><code class="xref py py-attr docutils literal notranslate"><span class="pre">block_on_close</span></code></a> attribute is <code class="docutils literal notranslate"><span class="pre">False</span></code>.</p>345</dd></dl>346 347<dl class="py attribute">348<dt class="sig sig-object py" id="socketserver.ThreadingMixIn.max_children">349<span class="sig-name descname"><span class="pre">max_children</span></span><a class="headerlink" href="#socketserver.ThreadingMixIn.max_children" title="Link to this definition">¶</a></dt>350<dd><p>Specify how many child processes will exist to handle requests at a time351for <code class="xref py py-class docutils literal notranslate"><span class="pre">ForkingMixIn</span></code>.  If the limit is reached,352new requests will wait until one child process has finished.</p>353</dd></dl>354 355<dl class="py attribute">356<dt class="sig sig-object py" id="socketserver.ThreadingMixIn.daemon_threads">357<span class="sig-name descname"><span class="pre">daemon_threads</span></span><a class="headerlink" href="#socketserver.ThreadingMixIn.daemon_threads" title="Link to this definition">¶</a></dt>358<dd><p>For <code class="xref py py-class docutils literal notranslate"><span class="pre">ThreadingMixIn</span></code> use daemonic threads by setting359<a class="reference internal" href="#socketserver.ThreadingMixIn.daemon_threads" title="socketserver.ThreadingMixIn.daemon_threads"><code class="xref py py-data docutils literal notranslate"><span class="pre">ThreadingMixIn.daemon_threads</span></code></a>360to <code class="docutils literal notranslate"><span class="pre">True</span></code> to not wait until threads complete.</p>361</dd></dl>362 363<div class="versionchanged">364<p><span class="versionmodified changed">Changed in version 3.7: </span><a class="reference internal" href="#socketserver.BaseServer.server_close" title="socketserver.BaseServer.server_close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ForkingMixIn.server_close</span></code></a> and365<code class="xref py py-meth docutils literal notranslate"><span class="pre">ThreadingMixIn.server_close</span></code> now waits until all366child processes and non-daemonic threads complete.367Add a new <a class="reference internal" href="#socketserver.ThreadingMixIn.block_on_close" title="socketserver.ThreadingMixIn.block_on_close"><code class="xref py py-attr docutils literal notranslate"><span class="pre">ForkingMixIn.block_on_close</span></code></a> class368attribute to opt-in for the pre-3.7 behaviour.</p>369</div>370</dd></dl>371 372<dl class="py class">373<dt class="sig sig-object py" id="socketserver.ForkingTCPServer">374<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">ForkingTCPServer</span></span><a class="headerlink" href="#socketserver.ForkingTCPServer" title="Link to this definition">¶</a></dt>375<dt class="sig sig-object py" id="socketserver.ForkingUDPServer">376<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">ForkingUDPServer</span></span><a class="headerlink" href="#socketserver.ForkingUDPServer" title="Link to this definition">¶</a></dt>377<dt class="sig sig-object py" id="socketserver.ThreadingTCPServer">378<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">ThreadingTCPServer</span></span><a class="headerlink" href="#socketserver.ThreadingTCPServer" title="Link to this definition">¶</a></dt>379<dt class="sig sig-object py" id="socketserver.ThreadingUDPServer">380<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">ThreadingUDPServer</span></span><a class="headerlink" href="#socketserver.ThreadingUDPServer" title="Link to this definition">¶</a></dt>381<dt class="sig sig-object py" id="socketserver.ForkingUnixStreamServer">382<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">ForkingUnixStreamServer</span></span><a class="headerlink" href="#socketserver.ForkingUnixStreamServer" title="Link to this definition">¶</a></dt>383<dt class="sig sig-object py" id="socketserver.ForkingUnixDatagramServer">384<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">ForkingUnixDatagramServer</span></span><a class="headerlink" href="#socketserver.ForkingUnixDatagramServer" title="Link to this definition">¶</a></dt>385<dt class="sig sig-object py" id="socketserver.ThreadingUnixStreamServer">386<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">ThreadingUnixStreamServer</span></span><a class="headerlink" href="#socketserver.ThreadingUnixStreamServer" title="Link to this definition">¶</a></dt>387<dt class="sig sig-object py" id="socketserver.ThreadingUnixDatagramServer">388<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">ThreadingUnixDatagramServer</span></span><a class="headerlink" href="#socketserver.ThreadingUnixDatagramServer" title="Link to this definition">¶</a></dt>389<dd><p>These classes are pre-defined using the mix-in classes.</p>390</dd></dl>391 392<div class="versionadded">393<p><span class="versionmodified added">Added in version 3.12: </span>The <code class="docutils literal notranslate"><span class="pre">ForkingUnixStreamServer</span></code> and <code class="docutils literal notranslate"><span class="pre">ForkingUnixDatagramServer</span></code> classes394were added.</p>395</div>396<p>To implement a service, you must derive a class from <a class="reference internal" href="#socketserver.BaseRequestHandler" title="socketserver.BaseRequestHandler"><code class="xref py py-class docutils literal notranslate"><span class="pre">BaseRequestHandler</span></code></a>397and redefine its <a class="reference internal" href="#socketserver.BaseRequestHandler.handle" title="socketserver.BaseRequestHandler.handle"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle()</span></code></a> method.398You can then run various versions of399the service by combining one of the server classes with your request handler400class.  The request handler class must be different for datagram or stream401services.  This can be hidden by using the handler subclasses402<a class="reference internal" href="#socketserver.StreamRequestHandler" title="socketserver.StreamRequestHandler"><code class="xref py py-class docutils literal notranslate"><span class="pre">StreamRequestHandler</span></code></a> or <a class="reference internal" href="#socketserver.DatagramRequestHandler" title="socketserver.DatagramRequestHandler"><code class="xref py py-class docutils literal notranslate"><span class="pre">DatagramRequestHandler</span></code></a>.</p>403<p>Of course, you still have to use your head!  For instance, it makes no sense to404use a forking server if the service contains state in memory that can be405modified by different requests, since the modifications in the child process406would never reach the initial state kept in the parent process and passed to407each child.  In this case, you can use a threading server, but you will probably408have to use locks to protect the integrity of the shared data.</p>409<p>On the other hand, if you are building an HTTP server where all data is stored410externally (for instance, in the file system), a synchronous class will411essentially render the service “deaf” while one request is being handled –412which may be for a very long time if a client is slow to receive all the data it413has requested.  Here a threading or forking server is appropriate.</p>414<p>In some cases, it may be appropriate to process part of a request synchronously,415but to finish processing in a forked child depending on the request data.  This416can be implemented by using a synchronous server and doing an explicit fork in417the request handler class <a class="reference internal" href="#socketserver.BaseRequestHandler.handle" title="socketserver.BaseRequestHandler.handle"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle()</span></code></a> method.</p>418<p>Another approach to handling multiple simultaneous requests in an environment419that supports neither threads nor <a class="reference internal" href="os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal notranslate"><span class="pre">fork()</span></code></a> (or where these are too420expensive or inappropriate for the service) is to maintain an explicit table of421partially finished requests and to use <a class="reference internal" href="selectors.html#module-selectors" title="selectors: High-level I/O multiplexing."><code class="xref py py-mod docutils literal notranslate"><span class="pre">selectors</span></code></a> to decide which422request to work on next (or whether to handle a new incoming request).  This is423particularly important for stream services where each client can potentially be424connected for a long time (if threads or subprocesses cannot be used).</p>425</section>426<section id="server-objects">427<h2>Server Objects<a class="headerlink" href="#server-objects" title="Link to this heading">¶</a></h2>428<dl class="py class">429<dt class="sig sig-object py" id="socketserver.BaseServer">430<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">BaseServer</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">server_address</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">RequestHandlerClass</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseServer" title="Link to this definition">¶</a></dt>431<dd><p>This is the superclass of all Server objects in the module.  It defines the432interface, given below, but does not implement most of the methods, which is433done in subclasses.  The two parameters are stored in the respective434<a class="reference internal" href="#socketserver.BaseServer.server_address" title="socketserver.BaseServer.server_address"><code class="xref py py-attr docutils literal notranslate"><span class="pre">server_address</span></code></a> and <a class="reference internal" href="#socketserver.BaseServer.RequestHandlerClass" title="socketserver.BaseServer.RequestHandlerClass"><code class="xref py py-attr docutils literal notranslate"><span class="pre">RequestHandlerClass</span></code></a> attributes.</p>435<dl class="py method">436<dt class="sig sig-object py" id="socketserver.BaseServer.fileno">437<span class="sig-name descname"><span class="pre">fileno</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseServer.fileno" title="Link to this definition">¶</a></dt>438<dd><p>Return an integer file descriptor for the socket on which the server is439listening.  This function is most commonly passed to <a class="reference internal" href="selectors.html#module-selectors" title="selectors: High-level I/O multiplexing."><code class="xref py py-mod docutils literal notranslate"><span class="pre">selectors</span></code></a>, to440allow monitoring multiple servers in the same process.</p>441</dd></dl>442 443<dl class="py method">444<dt class="sig sig-object py" id="socketserver.BaseServer.handle_request">445<span class="sig-name descname"><span class="pre">handle_request</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseServer.handle_request" title="Link to this definition">¶</a></dt>446<dd><p>Process a single request.  This function calls the following methods in447order: <a class="reference internal" href="#socketserver.BaseServer.get_request" title="socketserver.BaseServer.get_request"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_request()</span></code></a>, <a class="reference internal" href="#socketserver.BaseServer.verify_request" title="socketserver.BaseServer.verify_request"><code class="xref py py-meth docutils literal notranslate"><span class="pre">verify_request()</span></code></a>, and448<a class="reference internal" href="#socketserver.BaseServer.process_request" title="socketserver.BaseServer.process_request"><code class="xref py py-meth docutils literal notranslate"><span class="pre">process_request()</span></code></a>.  If the user-provided449<a class="reference internal" href="#socketserver.BaseRequestHandler.handle" title="socketserver.BaseRequestHandler.handle"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle()</span></code></a> method of the450handler class raises an exception, the server’s <a class="reference internal" href="#socketserver.BaseServer.handle_error" title="socketserver.BaseServer.handle_error"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle_error()</span></code></a> method451will be called.  If no request is received within <a class="reference internal" href="#socketserver.BaseServer.timeout" title="socketserver.BaseServer.timeout"><code class="xref py py-attr docutils literal notranslate"><span class="pre">timeout</span></code></a>452seconds, <a class="reference internal" href="#socketserver.BaseServer.handle_timeout" title="socketserver.BaseServer.handle_timeout"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle_timeout()</span></code></a> will be called and <code class="xref py py-meth docutils literal notranslate"><span class="pre">handle_request()</span></code>453will return.</p>454</dd></dl>455 456<dl class="py method">457<dt class="sig sig-object py" id="socketserver.BaseServer.serve_forever">458<span class="sig-name descname"><span class="pre">serve_forever</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">poll_interval</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0.5</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseServer.serve_forever" title="Link to this definition">¶</a></dt>459<dd><p>Handle requests until an explicit <a class="reference internal" href="#socketserver.BaseServer.shutdown" title="socketserver.BaseServer.shutdown"><code class="xref py py-meth docutils literal notranslate"><span class="pre">shutdown()</span></code></a> request.  Poll for460shutdown every <em>poll_interval</em> seconds.461Ignores the <a class="reference internal" href="#socketserver.BaseServer.timeout" title="socketserver.BaseServer.timeout"><code class="xref py py-attr docutils literal notranslate"><span class="pre">timeout</span></code></a> attribute.  It462also calls <a class="reference internal" href="#socketserver.BaseServer.service_actions" title="socketserver.BaseServer.service_actions"><code class="xref py py-meth docutils literal notranslate"><span class="pre">service_actions()</span></code></a>, which may be used by a subclass or mixin463to provide actions specific to a given service.  For example, the464<a class="reference internal" href="#socketserver.ForkingMixIn" title="socketserver.ForkingMixIn"><code class="xref py py-class docutils literal notranslate"><span class="pre">ForkingMixIn</span></code></a> class uses <code class="xref py py-meth docutils literal notranslate"><span class="pre">service_actions()</span></code> to clean up zombie465child processes.</p>466<div class="versionchanged">467<p><span class="versionmodified changed">Changed in version 3.3: </span>Added <code class="docutils literal notranslate"><span class="pre">service_actions</span></code> call to the <code class="docutils literal notranslate"><span class="pre">serve_forever</span></code> method.</p>468</div>469</dd></dl>470 471<dl class="py method">472<dt class="sig sig-object py" id="socketserver.BaseServer.service_actions">473<span class="sig-name descname"><span class="pre">service_actions</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseServer.service_actions" title="Link to this definition">¶</a></dt>474<dd><p>This is called in the <a class="reference internal" href="#socketserver.BaseServer.serve_forever" title="socketserver.BaseServer.serve_forever"><code class="xref py py-meth docutils literal notranslate"><span class="pre">serve_forever()</span></code></a> loop. This method can be475overridden by subclasses or mixin classes to perform actions specific to476a given service, such as cleanup actions.</p>477<div class="versionadded">478<p><span class="versionmodified added">Added in version 3.3.</span></p>479</div>480</dd></dl>481 482<dl class="py method">483<dt class="sig sig-object py" id="socketserver.BaseServer.shutdown">484<span class="sig-name descname"><span class="pre">shutdown</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseServer.shutdown" title="Link to this definition">¶</a></dt>485<dd><p>Tell the <a class="reference internal" href="#socketserver.BaseServer.serve_forever" title="socketserver.BaseServer.serve_forever"><code class="xref py py-meth docutils literal notranslate"><span class="pre">serve_forever()</span></code></a> loop to stop and wait until it does.486<code class="xref py py-meth docutils literal notranslate"><span class="pre">shutdown()</span></code> must be called while <code class="xref py py-meth docutils literal notranslate"><span class="pre">serve_forever()</span></code> is running in a487different thread otherwise it will deadlock.</p>488</dd></dl>489 490<dl class="py method">491<dt class="sig sig-object py" id="socketserver.BaseServer.server_close">492<span class="sig-name descname"><span class="pre">server_close</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseServer.server_close" title="Link to this definition">¶</a></dt>493<dd><p>Clean up the server. May be overridden.</p>494</dd></dl>495 496<dl class="py attribute">497<dt class="sig sig-object py" id="socketserver.BaseServer.address_family">498<span class="sig-name descname"><span class="pre">address_family</span></span><a class="headerlink" href="#socketserver.BaseServer.address_family" title="Link to this definition">¶</a></dt>499<dd><p>The family of protocols to which the server’s socket belongs.  Common500examples are <a class="reference internal" href="socket.html#socket.AF_INET" title="socket.AF_INET"><code class="xref py py-const docutils literal notranslate"><span class="pre">socket.AF_INET</span></code></a>, <a class="reference internal" href="socket.html#socket.AF_INET6" title="socket.AF_INET6"><code class="xref py py-const docutils literal notranslate"><span class="pre">socket.AF_INET6</span></code></a>, and501<a class="reference internal" href="socket.html#socket.AF_UNIX" title="socket.AF_UNIX"><code class="xref py py-const docutils literal notranslate"><span class="pre">socket.AF_UNIX</span></code></a>.  Subclass the TCP or UDP server classes in this502module with class attribute <code class="docutils literal notranslate"><span class="pre">address_family</span> <span class="pre">=</span> <span class="pre">AF_INET6</span></code> set if you503want IPv6 server classes.</p>504</dd></dl>505 506<dl class="py attribute">507<dt class="sig sig-object py" id="socketserver.BaseServer.RequestHandlerClass">508<span class="sig-name descname"><span class="pre">RequestHandlerClass</span></span><a class="headerlink" href="#socketserver.BaseServer.RequestHandlerClass" title="Link to this definition">¶</a></dt>509<dd><p>The user-provided request handler class; an instance of this class is created510for each request.</p>511</dd></dl>512 513<dl class="py attribute">514<dt class="sig sig-object py" id="socketserver.BaseServer.server_address">515<span class="sig-name descname"><span class="pre">server_address</span></span><a class="headerlink" href="#socketserver.BaseServer.server_address" title="Link to this definition">¶</a></dt>516<dd><p>The address on which the server is listening.  The format of addresses varies517depending on the protocol family;518see the documentation for the <a class="reference internal" href="socket.html#module-socket" title="socket: Low-level networking interface."><code class="xref py py-mod docutils literal notranslate"><span class="pre">socket</span></code></a> module519for details.  For internet protocols, this is a tuple containing a string giving520the address, and an integer port number: <code class="docutils literal notranslate"><span class="pre">('127.0.0.1',</span> <span class="pre">80)</span></code>, for example.</p>521</dd></dl>522 523<dl class="py attribute">524<dt class="sig sig-object py" id="socketserver.BaseServer.socket">525<span class="sig-name descname"><span class="pre">socket</span></span><a class="headerlink" href="#socketserver.BaseServer.socket" title="Link to this definition">¶</a></dt>526<dd><p>The socket object on which the server will listen for incoming requests.</p>527</dd></dl>528 529<p>The server classes support the following class variables:</p>530<dl class="py attribute">531<dt class="sig sig-object py" id="socketserver.BaseServer.allow_reuse_address">532<span class="sig-name descname"><span class="pre">allow_reuse_address</span></span><a class="headerlink" href="#socketserver.BaseServer.allow_reuse_address" title="Link to this definition">¶</a></dt>533<dd><p>Whether the server will allow the reuse of an address.  This defaults to534<a class="reference internal" href="constants.html#False" title="False"><code class="xref py py-const docutils literal notranslate"><span class="pre">False</span></code></a>, and can be set in subclasses to change the policy.</p>535</dd></dl>536 537<dl class="py attribute">538<dt class="sig sig-object py" id="socketserver.BaseServer.request_queue_size">539<span class="sig-name descname"><span class="pre">request_queue_size</span></span><a class="headerlink" href="#socketserver.BaseServer.request_queue_size" title="Link to this definition">¶</a></dt>540<dd><p>The size of the request queue.  If it takes a long time to process a single541request, any requests that arrive while the server is busy are placed into a542queue, up to <a class="reference internal" href="#socketserver.BaseServer.request_queue_size" title="socketserver.BaseServer.request_queue_size"><code class="xref py py-attr docutils literal notranslate"><span class="pre">request_queue_size</span></code></a> requests.  Once the queue is full,543further requests from clients will get a “Connection denied” error.  The default544value is usually 5, but this can be overridden by subclasses.</p>545</dd></dl>546 547<dl class="py attribute">548<dt class="sig sig-object py" id="socketserver.BaseServer.socket_type">549<span class="sig-name descname"><span class="pre">socket_type</span></span><a class="headerlink" href="#socketserver.BaseServer.socket_type" title="Link to this definition">¶</a></dt>550<dd><p>The type of socket used by the server; <a class="reference internal" href="socket.html#socket.SOCK_STREAM" title="socket.SOCK_STREAM"><code class="xref py py-const docutils literal notranslate"><span class="pre">socket.SOCK_STREAM</span></code></a> and551<a class="reference internal" href="socket.html#socket.SOCK_DGRAM" title="socket.SOCK_DGRAM"><code class="xref py py-const docutils literal notranslate"><span class="pre">socket.SOCK_DGRAM</span></code></a> are two common values.</p>552</dd></dl>553 554<dl class="py attribute">555<dt class="sig sig-object py" id="socketserver.BaseServer.timeout">556<span class="sig-name descname"><span class="pre">timeout</span></span><a class="headerlink" href="#socketserver.BaseServer.timeout" title="Link to this definition">¶</a></dt>557<dd><p>Timeout duration, measured in seconds, or <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a> if no timeout is558desired.  If <a class="reference internal" href="#socketserver.BaseServer.handle_request" title="socketserver.BaseServer.handle_request"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle_request()</span></code></a> receives no incoming requests within the559timeout period, the <a class="reference internal" href="#socketserver.BaseServer.handle_timeout" title="socketserver.BaseServer.handle_timeout"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle_timeout()</span></code></a> method is called.</p>560</dd></dl>561 562<p>There are various server methods that can be overridden by subclasses of base563server classes like <a class="reference internal" href="#socketserver.TCPServer" title="socketserver.TCPServer"><code class="xref py py-class docutils literal notranslate"><span class="pre">TCPServer</span></code></a>; these methods aren’t useful to external564users of the server object.</p>565<dl class="py method">566<dt class="sig sig-object py" id="socketserver.BaseServer.finish_request">567<span class="sig-name descname"><span class="pre">finish_request</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">request</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">client_address</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseServer.finish_request" title="Link to this definition">¶</a></dt>568<dd><p>Actually processes the request by instantiating <a class="reference internal" href="#socketserver.BaseServer.RequestHandlerClass" title="socketserver.BaseServer.RequestHandlerClass"><code class="xref py py-attr docutils literal notranslate"><span class="pre">RequestHandlerClass</span></code></a> and569calling its <a class="reference internal" href="#socketserver.BaseRequestHandler.handle" title="socketserver.BaseRequestHandler.handle"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle()</span></code></a> method.</p>570</dd></dl>571 572<dl class="py method">573<dt class="sig sig-object py" id="socketserver.BaseServer.get_request">574<span class="sig-name descname"><span class="pre">get_request</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseServer.get_request" title="Link to this definition">¶</a></dt>575<dd><p>Must accept a request from the socket, and return a 2-tuple containing the <em>new</em>576socket object to be used to communicate with the client, and the client’s577address.</p>578</dd></dl>579 580<dl class="py method">581<dt class="sig sig-object py" id="socketserver.BaseServer.handle_error">582<span class="sig-name descname"><span class="pre">handle_error</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">request</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">client_address</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseServer.handle_error" title="Link to this definition">¶</a></dt>583<dd><p>This function is called if the <a class="reference internal" href="#socketserver.BaseRequestHandler.handle" title="socketserver.BaseRequestHandler.handle"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle()</span></code></a>584method of a <a class="reference internal" href="#socketserver.BaseServer.RequestHandlerClass" title="socketserver.BaseServer.RequestHandlerClass"><code class="xref py py-attr docutils literal notranslate"><span class="pre">RequestHandlerClass</span></code></a> instance raises585an exception.  The default action is to print the traceback to586standard error and continue handling further requests.</p>587<div class="versionchanged">588<p><span class="versionmodified changed">Changed in version 3.6: </span>Now only called for exceptions derived from the <a class="reference internal" href="exceptions.html#Exception" title="Exception"><code class="xref py py-exc docutils literal notranslate"><span class="pre">Exception</span></code></a>589class.</p>590</div>591</dd></dl>592 593<dl class="py method">594<dt class="sig sig-object py" id="socketserver.BaseServer.handle_timeout">595<span class="sig-name descname"><span class="pre">handle_timeout</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseServer.handle_timeout" title="Link to this definition">¶</a></dt>596<dd><p>This function is called when the <a class="reference internal" href="#socketserver.BaseServer.timeout" title="socketserver.BaseServer.timeout"><code class="xref py py-attr docutils literal notranslate"><span class="pre">timeout</span></code></a> attribute has been set to a597value other than <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a> and the timeout period has passed with no598requests being received.  The default action for forking servers is599to collect the status of any child processes that have exited, while600in threading servers this method does nothing.</p>601</dd></dl>602 603<dl class="py method">604<dt class="sig sig-object py" id="socketserver.BaseServer.process_request">605<span class="sig-name descname"><span class="pre">process_request</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">request</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">client_address</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseServer.process_request" title="Link to this definition">¶</a></dt>606<dd><p>Calls <a class="reference internal" href="#socketserver.BaseServer.finish_request" title="socketserver.BaseServer.finish_request"><code class="xref py py-meth docutils literal notranslate"><span class="pre">finish_request()</span></code></a> to create an instance of the607<a class="reference internal" href="#socketserver.BaseServer.RequestHandlerClass" title="socketserver.BaseServer.RequestHandlerClass"><code class="xref py py-attr docutils literal notranslate"><span class="pre">RequestHandlerClass</span></code></a>.  If desired, this function can create a new process608or thread to handle the request; the <a class="reference internal" href="#socketserver.ForkingMixIn" title="socketserver.ForkingMixIn"><code class="xref py py-class docutils literal notranslate"><span class="pre">ForkingMixIn</span></code></a> and609<a class="reference internal" href="#socketserver.ThreadingMixIn" title="socketserver.ThreadingMixIn"><code class="xref py py-class docutils literal notranslate"><span class="pre">ThreadingMixIn</span></code></a> classes do this.</p>610</dd></dl>611 612<dl class="py method">613<dt class="sig sig-object py" id="socketserver.BaseServer.server_activate">614<span class="sig-name descname"><span class="pre">server_activate</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseServer.server_activate" title="Link to this definition">¶</a></dt>615<dd><p>Called by the server’s constructor to activate the server.  The default behavior616for a TCP server just invokes <a class="reference internal" href="socket.html#socket.socket.listen" title="socket.socket.listen"><code class="xref py py-meth docutils literal notranslate"><span class="pre">listen()</span></code></a>617on the server’s socket.  May be overridden.</p>618</dd></dl>619 620<dl class="py method">621<dt class="sig sig-object py" id="socketserver.BaseServer.server_bind">622<span class="sig-name descname"><span class="pre">server_bind</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseServer.server_bind" title="Link to this definition">¶</a></dt>623<dd><p>Called by the server’s constructor to bind the socket to the desired address.624May be overridden.</p>625</dd></dl>626 627<dl class="py method">628<dt class="sig sig-object py" id="socketserver.BaseServer.verify_request">629<span class="sig-name descname"><span class="pre">verify_request</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">request</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">client_address</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseServer.verify_request" title="Link to this definition">¶</a></dt>630<dd><p>Must return a Boolean value; if the value is <a class="reference internal" href="constants.html#True" title="True"><code class="xref py py-const docutils literal notranslate"><span class="pre">True</span></code></a>, the request will631be processed, and if it’s <a class="reference internal" href="constants.html#False" title="False"><code class="xref py py-const docutils literal notranslate"><span class="pre">False</span></code></a>, the request will be denied.  This632function can be overridden to implement access controls for a server. The633default implementation always returns <code class="xref py py-const docutils literal notranslate"><span class="pre">True</span></code>.</p>634</dd></dl>635 636<div class="versionchanged">637<p><span class="versionmodified changed">Changed in version 3.6: </span>Support for the <a class="reference internal" href="../glossary.html#term-context-manager"><span class="xref std std-term">context manager</span></a> protocol was added.  Exiting the638context manager is equivalent to calling <a class="reference internal" href="#socketserver.BaseServer.server_close" title="socketserver.BaseServer.server_close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">server_close()</span></code></a>.</p>639</div>640</dd></dl>641 642</section>643<section id="request-handler-objects">644<h2>Request Handler Objects<a class="headerlink" href="#request-handler-objects" title="Link to this heading">¶</a></h2>645<dl class="py class">646<dt class="sig sig-object py" id="socketserver.BaseRequestHandler">647<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">BaseRequestHandler</span></span><a class="headerlink" href="#socketserver.BaseRequestHandler" title="Link to this definition">¶</a></dt>648<dd><p>This is the superclass of all request handler objects.  It defines649the interface, given below.  A concrete request handler subclass must650define a new <a class="reference internal" href="#socketserver.BaseRequestHandler.handle" title="socketserver.BaseRequestHandler.handle"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle()</span></code></a> method, and can override any of651the other methods.  A new instance of the subclass is created for each652request.</p>653<dl class="py method">654<dt class="sig sig-object py" id="socketserver.BaseRequestHandler.setup">655<span class="sig-name descname"><span class="pre">setup</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseRequestHandler.setup" title="Link to this definition">¶</a></dt>656<dd><p>Called before the <a class="reference internal" href="#socketserver.BaseRequestHandler.handle" title="socketserver.BaseRequestHandler.handle"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle()</span></code></a> method to perform any initialization actions657required.  The default implementation does nothing.</p>658</dd></dl>659 660<dl class="py method">661<dt class="sig sig-object py" id="socketserver.BaseRequestHandler.handle">662<span class="sig-name descname"><span class="pre">handle</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseRequestHandler.handle" title="Link to this definition">¶</a></dt>663<dd><p>This function must do all the work required to service a request.  The664default implementation does nothing.  Several instance attributes are665available to it; the request is available as <a class="reference internal" href="#socketserver.BaseRequestHandler.request" title="socketserver.BaseRequestHandler.request"><code class="xref py py-attr docutils literal notranslate"><span class="pre">request</span></code></a>; the client666address as <a class="reference internal" href="#socketserver.BaseRequestHandler.client_address" title="socketserver.BaseRequestHandler.client_address"><code class="xref py py-attr docutils literal notranslate"><span class="pre">client_address</span></code></a>; and the server instance as667<a class="reference internal" href="#socketserver.BaseRequestHandler.server" title="socketserver.BaseRequestHandler.server"><code class="xref py py-attr docutils literal notranslate"><span class="pre">server</span></code></a>, in case it needs access to per-server information.</p>668<p>The type of <a class="reference internal" href="#socketserver.BaseRequestHandler.request" title="socketserver.BaseRequestHandler.request"><code class="xref py py-attr docutils literal notranslate"><span class="pre">request</span></code></a> is different for datagram or stream669services.  For stream services, <code class="xref py py-attr docutils literal notranslate"><span class="pre">request</span></code> is a socket object; for670datagram services, <code class="xref py py-attr docutils literal notranslate"><span class="pre">request</span></code> is a pair of string and socket.</p>671</dd></dl>672 673<dl class="py method">674<dt class="sig sig-object py" id="socketserver.BaseRequestHandler.finish">675<span class="sig-name descname"><span class="pre">finish</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#socketserver.BaseRequestHandler.finish" title="Link to this definition">¶</a></dt>676<dd><p>Called after the <a class="reference internal" href="#socketserver.BaseRequestHandler.handle" title="socketserver.BaseRequestHandler.handle"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle()</span></code></a> method to perform any clean-up actions677required.  The default implementation does nothing.  If <a class="reference internal" href="#socketserver.BaseRequestHandler.setup" title="socketserver.BaseRequestHandler.setup"><code class="xref py py-meth docutils literal notranslate"><span class="pre">setup()</span></code></a>678raises an exception, this function will not be called.</p>679</dd></dl>680 681<dl class="py attribute">682<dt class="sig sig-object py" id="socketserver.BaseRequestHandler.request">683<span class="sig-name descname"><span class="pre">request</span></span><a class="headerlink" href="#socketserver.BaseRequestHandler.request" title="Link to this definition">¶</a></dt>684<dd><p>The <em>new</em> <a class="reference internal" href="socket.html#socket.socket" title="socket.socket"><code class="xref py py-class docutils literal notranslate"><span class="pre">socket.socket</span></code></a> object685to be used to communicate with the client.</p>686</dd></dl>687 688<dl class="py attribute">689<dt class="sig sig-object py" id="socketserver.BaseRequestHandler.client_address">690<span class="sig-name descname"><span class="pre">client_address</span></span><a class="headerlink" href="#socketserver.BaseRequestHandler.client_address" title="Link to this definition">¶</a></dt>691<dd><p>Client address returned by <a class="reference internal" href="#socketserver.BaseServer.get_request" title="socketserver.BaseServer.get_request"><code class="xref py py-meth docutils literal notranslate"><span class="pre">BaseServer.get_request()</span></code></a>.</p>692</dd></dl>693 694<dl class="py attribute">695<dt class="sig sig-object py" id="socketserver.BaseRequestHandler.server">696<span class="sig-name descname"><span class="pre">server</span></span><a class="headerlink" href="#socketserver.BaseRequestHandler.server" title="Link to this definition">¶</a></dt>697<dd><p><a class="reference internal" href="#socketserver.BaseServer" title="socketserver.BaseServer"><code class="xref py py-class docutils literal notranslate"><span class="pre">BaseServer</span></code></a> object used for handling the request.</p>698</dd></dl>699 700</dd></dl>701 702<dl class="py class">703<dt class="sig sig-object py" id="socketserver.StreamRequestHandler">704<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">StreamRequestHandler</span></span><a class="headerlink" href="#socketserver.StreamRequestHandler" title="Link to this definition">¶</a></dt>705<dt class="sig sig-object py" id="socketserver.DatagramRequestHandler">706<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">socketserver.</span></span><span class="sig-name descname"><span class="pre">DatagramRequestHandler</span></span><a class="headerlink" href="#socketserver.DatagramRequestHandler" title="Link to this definition">¶</a></dt>707<dd><p>These <a class="reference internal" href="#socketserver.BaseRequestHandler" title="socketserver.BaseRequestHandler"><code class="xref py py-class docutils literal notranslate"><span class="pre">BaseRequestHandler</span></code></a> subclasses override the708<a class="reference internal" href="#socketserver.BaseRequestHandler.setup" title="socketserver.BaseRequestHandler.setup"><code class="xref py py-meth docutils literal notranslate"><span class="pre">setup()</span></code></a> and <a class="reference internal" href="#socketserver.BaseRequestHandler.finish" title="socketserver.BaseRequestHandler.finish"><code class="xref py py-meth docutils literal notranslate"><span class="pre">finish()</span></code></a>709methods, and provide <a class="reference internal" href="#socketserver.DatagramRequestHandler.rfile" title="socketserver.DatagramRequestHandler.rfile"><code class="xref py py-attr docutils literal notranslate"><span class="pre">rfile</span></code></a> and <a class="reference internal" href="#socketserver.DatagramRequestHandler.wfile" title="socketserver.DatagramRequestHandler.wfile"><code class="xref py py-attr docutils literal notranslate"><span class="pre">wfile</span></code></a> attributes.</p>710<dl class="py attribute">711<dt class="sig sig-object py" id="socketserver.DatagramRequestHandler.rfile">712<span class="sig-name descname"><span class="pre">rfile</span></span><a class="headerlink" href="#socketserver.DatagramRequestHandler.rfile" title="Link to this definition">¶</a></dt>713<dd><p>A file object from which receives the request is read.714Support the <a class="reference internal" href="io.html#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.BufferedIOBase</span></code></a> readable interface.</p>715</dd></dl>716 717<dl class="py attribute">718<dt class="sig sig-object py" id="socketserver.DatagramRequestHandler.wfile">719<span class="sig-name descname"><span class="pre">wfile</span></span><a class="headerlink" href="#socketserver.DatagramRequestHandler.wfile" title="Link to this definition">¶</a></dt>720<dd><p>A file object to which the reply is written.721Support the <a class="reference internal" href="io.html#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.BufferedIOBase</span></code></a> writable interface</p>722</dd></dl>723 724<div class="versionchanged">725<p><span class="versionmodified changed">Changed in version 3.6: </span><a class="reference internal" href="#socketserver.DatagramRequestHandler.wfile" title="socketserver.DatagramRequestHandler.wfile"><code class="xref py py-attr docutils literal notranslate"><span class="pre">wfile</span></code></a> also supports the726<a class="reference internal" href="io.html#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.BufferedIOBase</span></code></a> writable interface.</p>727</div>728</dd></dl>729 730</section>731<section id="examples">732<h2>Examples<a class="headerlink" href="#examples" title="Link to this heading">¶</a></h2>733<section id="socketserver-tcpserver-example">734<h3><a class="reference internal" href="#socketserver.TCPServer" title="socketserver.TCPServer"><code class="xref py py-class docutils literal notranslate"><span class="pre">socketserver.TCPServer</span></code></a> Example<a class="headerlink" href="#socketserver-tcpserver-example" title="Link to this heading">¶</a></h3>735<p>This is the server side:</p>736<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">socketserver</span>737 738<span class="k">class</span><span class="w"> </span><span class="nc">MyTCPHandler</span><span class="p">(</span><span class="n">socketserver</span><span class="o">.</span><span class="n">BaseRequestHandler</span><span class="p">):</span>739<span class="w">    </span><span class="sd">&quot;&quot;&quot;</span>740<span class="sd">    The request handler class for our server.</span>741 742<span class="sd">    It is instantiated once per connection to the server, and must</span>743<span class="sd">    override the handle() method to implement communication to the</span>744<span class="sd">    client.</span>745<span class="sd">    &quot;&quot;&quot;</span>746 747    <span class="k">def</span><span class="w"> </span><span class="nf">handle</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>748        <span class="c1"># self.request is the TCP socket connected to the client</span>749        <span class="n">pieces</span> <span class="o">=</span> <span class="p">[</span><span class="sa">b</span><span class="s1">&#39;&#39;</span><span class="p">]</span>750        <span class="n">total</span> <span class="o">=</span> <span class="mi">0</span>751        <span class="k">while</span> <span class="sa">b</span><span class="s1">&#39;</span><span class="se">\n</span><span class="s1">&#39;</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">pieces</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">]</span> <span class="ow">and</span> <span class="n">total</span> <span class="o">&lt;</span> <span class="mi">10_000</span><span class="p">:</span>752            <span class="n">pieces</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">request</span><span class="o">.</span><span class="n">recv</span><span class="p">(</span><span class="mi">2000</span><span class="p">))</span>753            <span class="n">total</span> <span class="o">+=</span> <span class="nb">len</span><span class="p">(</span><span class="n">pieces</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">])</span>754        <span class="bp">self</span><span class="o">.</span><span class="n">data</span> <span class="o">=</span> <span class="sa">b</span><span class="s1">&#39;&#39;</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">pieces</span><span class="p">)</span>755        <span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">&quot;Received from </span><span class="si">{</span><span class="bp">self</span><span class="o">.</span><span class="n">client_address</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="si">}</span><span class="s2">:&quot;</span><span class="p">)</span>756        <span class="nb">print</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">data</span><span class="o">.</span><span class="n">decode</span><span class="p">(</span><span class="s2">&quot;utf-8&quot;</span><span class="p">))</span>757        <span class="c1"># just send back the same data, but upper-cased</span>758        <span class="bp">self</span><span class="o">.</span><span class="n">request</span><span class="o">.</span><span class="n">sendall</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">data</span><span class="o">.</span><span class="n">upper</span><span class="p">())</span>759        <span class="c1"># after we return, the socket will be closed.</span>760 761<span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s2">&quot;__main__&quot;</span><span class="p">:</span>762    <span class="n">HOST</span><span class="p">,</span> <span class="n">PORT</span> <span class="o">=</span> <span class="s2">&quot;localhost&quot;</span><span class="p">,</span> <span class="mi">9999</span>763 764    <span class="c1"># Create the server, binding to localhost on port 9999</span>765    <span class="k">with</span> <span class="n">socketserver</span><span class="o">.</span><span class="n">TCPServer</span><span class="p">((</span><span class="n">HOST</span><span class="p">,</span> <span class="n">PORT</span><span class="p">),</span> <span class="n">MyTCPHandler</span><span class="p">)</span> <span class="k">as</span> <span class="n">server</span><span class="p">:</span>766        <span class="c1"># Activate the server; this will keep running until you</span>767        <span class="c1"># interrupt the program with Ctrl-C</span>768        <span class="n">server</span><span class="o">.</span><span class="n">serve_forever</span><span class="p">()</span>769</pre></div>770</div>771<p>An alternative request handler class that makes use of streams (file-like772objects that simplify communication by providing the standard file interface):</p>773<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">class</span><span class="w"> </span><span class="nc">MyTCPHandler</span><span class="p">(</span><span class="n">socketserver</span><span class="o">.</span><span class="n">StreamRequestHandler</span><span class="p">):</span>774 775    <span class="k">def</span><span class="w"> </span><span class="nf">handle</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>776        <span class="c1"># self.rfile is a file-like object created by the handler.</span>777        <span class="c1"># We can now use e.g. readline() instead of raw recv() calls.</span>778        <span class="c1"># We limit ourselves to 10000 bytes to avoid abuse by the sender.</span>779        <span class="bp">self</span><span class="o">.</span><span class="n">data</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">rfile</span><span class="o">.</span><span class="n">readline</span><span class="p">(</span><span class="mi">10000</span><span class="p">)</span><span class="o">.</span><span class="n">rstrip</span><span class="p">()</span>780        <span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">&quot;</span><span class="si">{</span><span class="bp">self</span><span class="o">.</span><span class="n">client_address</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="si">}</span><span class="s2"> wrote:&quot;</span><span class="p">)</span>781        <span class="nb">print</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">data</span><span class="o">.</span><span class="n">decode</span><span class="p">(</span><span class="s2">&quot;utf-8&quot;</span><span class="p">))</span>782        <span class="c1"># Likewise, self.wfile is a file-like object used to write back</span>783        <span class="c1"># to the client</span>784        <span class="bp">self</span><span class="o">.</span><span class="n">wfile</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">data</span><span class="o">.</span><span class="n">upper</span><span class="p">())</span>785</pre></div>786</div>787<p>The difference is that the <code class="docutils literal notranslate"><span class="pre">readline()</span></code> call in the second handler will call788<code class="docutils literal notranslate"><span class="pre">recv()</span></code> multiple times until it encounters a newline character, while the789first handler had to use a <code class="docutils literal notranslate"><span class="pre">recv()</span></code> loop to accumulate data until a790newline itself.  If it had just used a single <code class="docutils literal notranslate"><span class="pre">recv()</span></code> without the loop it791would just have returned what has been received so far from the client.792TCP is stream based: data arrives in the order it was sent, but there is no793correlation between client <code class="docutils literal notranslate"><span class="pre">send()</span></code> or <code class="docutils literal notranslate"><span class="pre">sendall()</span></code> calls and the number794of <code class="docutils literal notranslate"><span class="pre">recv()</span></code> calls on the server required to receive it.</p>795<p>This is the client side:</p>796<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">socket</span>797<span class="kn">import</span><span class="w"> </span><span class="nn">sys</span>798 799<span class="n">HOST</span><span class="p">,</span> <span class="n">PORT</span> <span class="o">=</span> <span class="s2">&quot;localhost&quot;</span><span class="p">,</span> <span class="mi">9999</span>800<span class="n">data</span> <span class="o">=</span> <span class="s2">&quot; &quot;</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">argv</span><span class="p">[</span><span class="mi">1</span><span class="p">:])</span>801 802<span class="c1"># Create a socket (SOCK_STREAM means a TCP socket)</span>803<span class="k">with</span> <span class="n">socket</span><span class="o">.</span><span class="n">socket</span><span class="p">(</span><span class="n">socket</span><span class="o">.</span><span class="n">AF_INET</span><span class="p">,</span> <span class="n">socket</span><span class="o">.</span><span class="n">SOCK_STREAM</span><span class="p">)</span> <span class="k">as</span> <span class="n">sock</span><span class="p">:</span>804    <span class="c1"># Connect to server and send data</span>805    <span class="n">sock</span><span class="o">.</span><span class="n">connect</span><span class="p">((</span><span class="n">HOST</span><span class="p">,</span> <span class="n">PORT</span><span class="p">))</span>806    <span class="n">sock</span><span class="o">.</span><span class="n">sendall</span><span class="p">(</span><span class="nb">bytes</span><span class="p">(</span><span class="n">data</span><span class="p">,</span> <span class="s2">&quot;utf-8&quot;</span><span class="p">))</span>807    <span class="n">sock</span><span class="o">.</span><span class="n">sendall</span><span class="p">(</span><span class="sa">b</span><span class="s2">&quot;</span><span class="se">\n</span><span class="s2">&quot;</span><span class="p">)</span>808 809    <span class="c1"># Receive data from the server and shut down</span>810    <span class="n">received</span> <span class="o">=</span> <span class="nb">str</span><span class="p">(</span><span class="n">sock</span><span class="o">.</span><span class="n">recv</span><span class="p">(</span><span class="mi">1024</span><span class="p">),</span> <span class="s2">&quot;utf-8&quot;</span><span class="p">)</span>811 812<span class="nb">print</span><span class="p">(</span><span class="s2">&quot;Sent:    &quot;</span><span class="p">,</span> <span class="n">data</span><span class="p">)</span>813<span class="nb">print</span><span class="p">(</span><span class="s2">&quot;Received:&quot;</span><span class="p">,</span> <span class="n">received</span><span class="p">)</span>814</pre></div>815</div>816<p>The output of the example should look something like this:</p>817<p>Server:</p>818<div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>python<span class="w"> </span>TCPServer.py819<span class="go">127.0.0.1 wrote:</span>820<span class="go">b&#39;hello world with TCP&#39;</span>821<span class="go">127.0.0.1 wrote:</span>822<span class="go">b&#39;python is nice&#39;</span>823</pre></div>824</div>825<p>Client:</p>826<div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>python<span class="w"> </span>TCPClient.py<span class="w"> </span>hello<span class="w"> </span>world<span class="w"> </span>with<span class="w"> </span>TCP827<span class="go">Sent:     hello world with TCP</span>828<span class="go">Received: HELLO WORLD WITH TCP</span>829<span class="gp">$ </span>python<span class="w"> </span>TCPClient.py<span class="w"> </span>python<span class="w"> </span>is<span class="w"> </span>nice830<span class="go">Sent:     python is nice</span>831<span class="go">Received: PYTHON IS NICE</span>832</pre></div>833</div>834</section>835<section id="socketserver-udpserver-example">836<h3><a class="reference internal" href="#socketserver.UDPServer" title="socketserver.UDPServer"><code class="xref py py-class docutils literal notranslate"><span class="pre">socketserver.UDPServer</span></code></a> Example<a class="headerlink" href="#socketserver-udpserver-example" title="Link to this heading">¶</a></h3>837<p>This is the server side:</p>838<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">socketserver</span>839 840<span class="k">class</span><span class="w"> </span><span class="nc">MyUDPHandler</span><span class="p">(</span><span class="n">socketserver</span><span class="o">.</span><span class="n">BaseRequestHandler</span><span class="p">):</span>841<span class="w">    </span><span class="sd">&quot;&quot;&quot;</span>842<span class="sd">    This class works similar to the TCP handler class, except that</span>843<span class="sd">    self.request consists of a pair of data and client socket, and since</span>844<span class="sd">    there is no connection the client address must be given explicitly</span>845<span class="sd">    when sending data back via sendto().</span>846<span class="sd">    &quot;&quot;&quot;</span>847 848    <span class="k">def</span><span class="w"> </span><span class="nf">handle</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>849        <span class="n">data</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">request</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">strip</span><span class="p">()</span>850        <span class="n">socket</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">request</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span>851        <span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">&quot;</span><span class="si">{</span><span class="bp">self</span><span class="o">.</span><span class="n">client_address</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="si">}</span><span class="s2"> wrote:&quot;</span><span class="p">)</span>852        <span class="nb">print</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>853        <span class="n">socket</span><span class="o">.</span><span class="n">sendto</span><span class="p">(</span><span class="n">data</span><span class="o">.</span><span class="n">upper</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">client_address</span><span class="p">)</span>854 855<span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s2">&quot;__main__&quot;</span><span class="p">:</span>856    <span class="n">HOST</span><span class="p">,</span> <span class="n">PORT</span> <span class="o">=</span> <span class="s2">&quot;localhost&quot;</span><span class="p">,</span> <span class="mi">9999</span>857    <span class="k">with</span> <span class="n">socketserver</span><span class="o">.</span><span class="n">UDPServer</span><span class="p">((</span><span class="n">HOST</span><span class="p">,</span> <span class="n">PORT</span><span class="p">),</span> <span class="n">MyUDPHandler</span><span class="p">)</span> <span class="k">as</span> <span class="n">server</span><span class="p">:</span>858        <span class="n">server</span><span class="o">.</span><span class="n">serve_forever</span><span class="p">()</span>859</pre></div>860</div>861<p>This is the client side:</p>862<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">socket</span>863<span class="kn">import</span><span class="w"> </span><span class="nn">sys</span>864 865<span class="n">HOST</span><span class="p">,</span> <span class="n">PORT</span> <span class="o">=</span> <span class="s2">&quot;localhost&quot;</span><span class="p">,</span> <span class="mi">9999</span>866<span class="n">data</span> <span class="o">=</span> <span class="s2">&quot; &quot;</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">argv</span><span class="p">[</span><span class="mi">1</span><span class="p">:])</span>867 868<span class="c1"># SOCK_DGRAM is the socket type to use for UDP sockets</span>869<span class="n">sock</span> <span class="o">=</span> <span class="n">socket</span><span class="o">.</span><span class="n">socket</span><span class="p">(</span><span class="n">socket</span><span class="o">.</span><span class="n">AF_INET</span><span class="p">,</span> <span class="n">socket</span><span class="o">.</span><span class="n">SOCK_DGRAM</span><span class="p">)</span>870 871<span class="c1"># As you can see, there is no connect() call; UDP has no connections.</span>872<span class="c1"># Instead, data is directly sent to the recipient via sendto().</span>873<span class="n">sock</span><span class="o">.</span><span class="n">sendto</span><span class="p">(</span><span class="nb">bytes</span><span class="p">(</span><span class="n">data</span> <span class="o">+</span> <span class="s2">&quot;</span><span class="se">\n</span><span class="s2">&quot;</span><span class="p">,</span> <span class="s2">&quot;utf-8&quot;</span><span class="p">),</span> <span class="p">(</span><span class="n">HOST</span><span class="p">,</span> <span class="n">PORT</span><span class="p">))</span>874<span class="n">received</span> <span class="o">=</span> <span class="nb">str</span><span class="p">(</span><span class="n">sock</span><span class="o">.</span><span class="n">recv</span><span class="p">(</span><span class="mi">1024</span><span class="p">),</span> <span class="s2">&quot;utf-8&quot;</span><span class="p">)</span>875 876<span class="nb">print</span><span class="p">(</span><span class="s2">&quot;Sent:    &quot;</span><span class="p">,</span> <span class="n">data</span><span class="p">)</span>877<span class="nb">print</span><span class="p">(</span><span class="s2">&quot;Received:&quot;</span><span class="p">,</span> <span class="n">received</span><span class="p">)</span>878</pre></div>879</div>880<p>The output of the example should look exactly like for the TCP server example.</p>881</section>882<section id="asynchronous-mixins">883<h3>Asynchronous Mixins<a class="headerlink" href="#asynchronous-mixins" title="Link to this heading">¶</a></h3>884<p>To build asynchronous handlers, use the <a class="reference internal" href="#socketserver.ThreadingMixIn" title="socketserver.ThreadingMixIn"><code class="xref py py-class docutils literal notranslate"><span class="pre">ThreadingMixIn</span></code></a> and885<a class="reference internal" href="#socketserver.ForkingMixIn" title="socketserver.ForkingMixIn"><code class="xref py py-class docutils literal notranslate"><span class="pre">ForkingMixIn</span></code></a> classes.</p>886<p>An example for the <a class="reference internal" href="#socketserver.ThreadingMixIn" title="socketserver.ThreadingMixIn"><code class="xref py py-class docutils literal notranslate"><span class="pre">ThreadingMixIn</span></code></a> class:</p>887<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">socket</span>888<span class="kn">import</span><span class="w"> </span><span class="nn">threading</span>889<span class="kn">import</span><span class="w"> </span><span class="nn">socketserver</span>890 891<span class="k">class</span><span class="w"> </span><span class="nc">ThreadedTCPRequestHandler</span><span class="p">(</span><span class="n">socketserver</span><span class="o">.</span><span class="n">BaseRequestHandler</span><span class="p">):</span>892 893    <span class="k">def</span><span class="w"> </span><span class="nf">handle</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>894        <span class="n">data</span> <span class="o">=</span> <span class="nb">str</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">request</span><span class="o">.</span><span class="n">recv</span><span class="p">(</span><span class="mi">1024</span><span class="p">),</span> <span class="s1">&#39;ascii&#39;</span><span class="p">)</span>895        <span class="n">cur_thread</span> <span class="o">=</span> <span class="n">threading</span><span class="o">.</span><span class="n">current_thread</span><span class="p">()</span>896        <span class="n">response</span> <span class="o">=</span> <span class="nb">bytes</span><span class="p">(</span><span class="s2">&quot;</span><span class="si">{}</span><span class="s2">: </span><span class="si">{}</span><span class="s2">&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">cur_thread</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">data</span><span class="p">),</span> <span class="s1">&#39;ascii&#39;</span><span class="p">)</span>897        <span class="bp">self</span><span class="o">.</span><span class="n">request</span><span class="o">.</span><span class="n">sendall</span><span class="p">(</span><span class="n">response</span><span class="p">)</span>898 899<span class="k">class</span><span class="w"> </span><span class="nc">ThreadedTCPServer</span><span class="p">(</span><span class="n">socketserver</span><span class="o">.</span><span class="n">ThreadingMixIn</span><span class="p">,</span> <span class="n">socketserver</span><span class="o">.</span><span class="n">TCPServer</span><span class="p">):</span>900    <span class="k">pass</span>901 902<span class="k">def</span><span class="w"> </span><span class="nf">client</span><span class="p">(</span><span class="n">ip</span><span class="p">,</span> <span class="n">port</span><span class="p">,</span> <span class="n">message</span><span class="p">):</span>903    <span class="k">with</span> <span class="n">socket</span><span class="o">.</span><span class="n">socket</span><span class="p">(</span><span class="n">socket</span><span class="o">.</span><span class="n">AF_INET</span><span class="p">,</span> <span class="n">socket</span><span class="o">.</span><span class="n">SOCK_STREAM</span><span class="p">)</span> <span class="k">as</span> <span class="n">sock</span><span class="p">:</span>904        <span class="n">sock</span><span class="o">.</span><span class="n">connect</span><span class="p">((</span><span class="n">ip</span><span class="p">,</span> <span class="n">port</span><span class="p">))</span>905        <span class="n">sock</span><span class="o">.</span><span class="n">sendall</span><span class="p">(</span><span class="nb">bytes</span><span class="p">(</span><span class="n">message</span><span class="p">,</span> <span class="s1">&#39;ascii&#39;</span><span class="p">))</span>906        <span class="n">response</span> <span class="o">=</span> <span class="nb">str</span><span class="p">(</span><span class="n">sock</span><span class="o">.</span><span class="n">recv</span><span class="p">(</span><span class="mi">1024</span><span class="p">),</span> <span class="s1">&#39;ascii&#39;</span><span class="p">)</span>907        <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;Received: </span><span class="si">{}</span><span class="s2">&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">response</span><span class="p">))</span>908 909<span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s2">&quot;__main__&quot;</span><span class="p">:</span>910    <span class="c1"># Port 0 means to select an arbitrary unused port</span>911    <span class="n">HOST</span><span class="p">,</span> <span class="n">PORT</span> <span class="o">=</span> <span class="s2">&quot;localhost&quot;</span><span class="p">,</span> <span class="mi">0</span>912 913    <span class="n">server</span> <span class="o">=</span> <span class="n">ThreadedTCPServer</span><span class="p">((</span><span class="n">HOST</span><span class="p">,</span> <span class="n">PORT</span><span class="p">),</span> <span class="n">ThreadedTCPRequestHandler</span><span class="p">)</span>914    <span class="k">with</span> <span class="n">server</span><span class="p">:</span>915        <span class="n">ip</span><span class="p">,</span> <span class="n">port</span> <span class="o">=</span> <span class="n">server</span><span class="o">.</span><span class="n">server_address</span>916 917        <span class="c1"># Start a thread with the server -- that thread will then start one</span>918        <span class="c1"># more thread for each request</span>919        <span class="n">server_thread</span> <span class="o">=</span> <span class="n">threading</span><span class="o">.</span><span class="n">Thread</span><span class="p">(</span><span class="n">target</span><span class="o">=</span><span class="n">server</span><span class="o">.</span><span class="n">serve_forever</span><span class="p">)</span>920        <span class="c1"># Exit the server thread when the main thread terminates</span>921        <span class="n">server_thread</span><span class="o">.</span><span class="n">daemon</span> <span class="o">=</span> <span class="kc">True</span>922        <span class="n">server_thread</span><span class="o">.</span><span class="n">start</span><span class="p">()</span>923        <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;Server loop running in thread:&quot;</span><span class="p">,</span> <span class="n">server_thread</span><span class="o">.</span><span class="n">name</span><span class="p">)</span>924 925        <span class="n">client</span><span class="p">(</span><span class="n">ip</span><span class="p">,</span> <span class="n">port</span><span class="p">,</span> <span class="s2">&quot;Hello World 1&quot;</span><span class="p">)</span>926        <span class="n">client</span><span class="p">(</span><span class="n">ip</span><span class="p">,</span> <span class="n">port</span><span class="p">,</span> <span class="s2">&quot;Hello World 2&quot;</span><span class="p">)</span>927        <span class="n">client</span><span class="p">(</span><span class="n">ip</span><span class="p">,</span> <span class="n">port</span><span class="p">,</span> <span class="s2">&quot;Hello World 3&quot;</span><span class="p">)</span>928 929        <span class="n">server</span><span class="o">.</span><span class="n">shutdown</span><span class="p">()</span>930</pre></div>931</div>932<p>The output of the example should look something like this:</p>933<div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>python<span class="w"> </span>ThreadedTCPServer.py934<span class="go">Server loop running in thread: Thread-1</span>935<span class="go">Received: Thread-2: Hello World 1</span>936<span class="go">Received: Thread-3: Hello World 2</span>937<span class="go">Received: Thread-4: Hello World 3</span>938</pre></div>939</div>940<p>The <a class="reference internal" href="#socketserver.ForkingMixIn" title="socketserver.ForkingMixIn"><code class="xref py py-class docutils literal notranslate"><span class="pre">ForkingMixIn</span></code></a> class is used in the same way, except that the server941will spawn a new process for each request.942Available only on POSIX platforms that support <a class="reference internal" href="os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal notranslate"><span class="pre">fork()</span></code></a>.</p>943</section>944</section>945</section>946 947 948            <div class="clearer"></div>949          </div>950        </div>951      </div>952      <div class="sphinxsidebar" role="navigation" aria-label="Main">953        <div class="sphinxsidebarwrapper">954  <div>955    <h3><a href="../contents.html">Table of Contents</a></h3>956    <ul>957<li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">socketserver</span></code> — A framework for network servers</a><ul>958<li><a class="reference internal" href="#server-creation-notes">Server Creation Notes</a></li>959<li><a class="reference internal" href="#server-objects">Server Objects</a></li>960<li><a class="reference internal" href="#request-handler-objects">Request Handler Objects</a></li>961<li><a class="reference internal" href="#examples">Examples</a><ul>962<li><a class="reference internal" href="#socketserver-tcpserver-example"><code class="xref py py-class docutils literal notranslate"><span class="pre">socketserver.TCPServer</span></code> Example</a></li>963<li><a class="reference internal" href="#socketserver-udpserver-example"><code class="xref py py-class docutils literal notranslate"><span class="pre">socketserver.UDPServer</span></code> Example</a></li>964<li><a class="reference internal" href="#asynchronous-mixins">Asynchronous Mixins</a></li>965</ul>966</li>967</ul>968</li>969</ul>970 971  </div>972  <div>973    <h4>Previous topic</h4>974    <p class="topless"><a href="uuid.html"975                          title="previous chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">uuid</span></code> — UUID objects according to <strong>RFC 9562</strong></a></p>976  </div>977  <div>978    <h4>Next topic</h4>979    <p class="topless"><a href="http.server.html"980                          title="next chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">http.server</span></code> — HTTP servers</a></p>981  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