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Edit:
/usr/share/doc/python2-docs/html/library/socketserver.html
(76430B)
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SocketServer — A framework for network servers — Python 2.7.16 documentation</title> <link rel="stylesheet" href="../_static/classic.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript" id="documentation_options" data-url_root="../" src="../_static/documentation_options.js"></script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/underscore.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <script type="text/javascript" src="../_static/sidebar.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python 2.7.16 documentation" href="../_static/opensearch.xml"/> <link rel="author" title="About these documents" href="../about.html" /> <link rel="index" title="Index" href="../genindex.html" /> <link rel="search" title="Search" href="../search.html" /> <link rel="copyright" title="Copyright" href="../copyright.html" /> <link rel="next" title="20.18. 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Internet Protocols and Support</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body" role="main"> <div class="section" id="module-SocketServer"> <span id="socketserver-a-framework-for-network-servers"></span><h1>20.17. <a class="reference internal" href="#module-SocketServer" title="SocketServer: A framework for network servers."><code class="xref py py-mod docutils literal notranslate"><span class="pre">SocketServer</span></code></a> — A framework for network servers<a class="headerlink" href="#module-SocketServer" title="Permalink to this headline">¶</a></h1> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The <a class="reference internal" href="#module-SocketServer" title="SocketServer: A framework for network servers."><code class="xref py py-mod docutils literal notranslate"><span class="pre">SocketServer</span></code></a> module has been renamed to <code class="xref py py-mod docutils literal notranslate"><span class="pre">socketserver</span></code> in Python 3. The <a class="reference internal" href="../glossary.html#term-2to3"><span class="xref std std-term">2to3</span></a> tool will automatically adapt imports when converting your sources to Python 3.</p> </div> <p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/2.7/Lib/SocketServer.py">Lib/SocketServer.py</a></p> <hr class="docutils" /> <p>The <a class="reference internal" href="#module-SocketServer" title="SocketServer: A framework for network servers."><code class="xref py py-mod docutils literal notranslate"><span class="pre">SocketServer</span></code></a> module simplifies the task of writing network servers.</p> <p>There are four basic concrete server classes:</p> <dl class="class"> <dt id="SocketServer.TCPServer"> <em class="property">class </em><code class="descclassname">SocketServer.</code><code class="descname">TCPServer</code><span class="sig-paren">(</span><em>server_address</em>, <em>RequestHandlerClass</em>, <em>bind_and_activate=True</em><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.TCPServer" title="Permalink to this definition">¶</a></dt> <dd><p>This uses the Internet TCP protocol, which provides for continuous streams of data between the client and server. If <em>bind_and_activate</em> is true, the constructor automatically attempts to invoke <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> and <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 to the <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> </dd></dl> <dl class="class"> <dt id="SocketServer.UDPServer"> <em class="property">class </em><code class="descclassname">SocketServer.</code><code class="descname">UDPServer</code><span class="sig-paren">(</span><em>server_address</em>, <em>RequestHandlerClass</em>, <em>bind_and_activate=True</em><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.UDPServer" title="Permalink to this definition">¶</a></dt> <dd><p>This uses datagrams, which are discrete packets of information that may arrive out of order or be lost while in transit. The parameters are the 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> </dd></dl> <dl class="class"> <dt id="SocketServer.UnixStreamServer"> <em class="property">class </em><code class="descclassname">SocketServer.</code><code class="descname">UnixStreamServer</code><span class="sig-paren">(</span><em>server_address</em>, <em>RequestHandlerClass</em>, <em>bind_and_activate=True</em><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.UnixStreamServer" title="Permalink to this definition">¶</a></dt> <dt id="SocketServer.UnixDatagramServer"> <em class="property">class </em><code class="descclassname">SocketServer.</code><code class="descname">UnixDatagramServer</code><span class="sig-paren">(</span><em>server_address</em>, <em>RequestHandlerClass</em>, <em>bind_and_activate=True</em><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.UnixDatagramServer" title="Permalink to this definition">¶</a></dt> <dd><p>These more infrequently used classes are similar to the TCP and UDP classes, but use Unix domain sockets; they’re not available on non-Unix platforms. The parameters are the 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> </dd></dl> <p>These four classes process requests <em class="dfn">synchronously</em>; each request must be completed before the next request can be started. This isn’t suitable if each request takes a long time to complete, because it requires a lot of computation, or because it returns a lot of data which the client is slow to process. The solution is to create a separate process or thread to handle each 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> 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 to support asynchronous behaviour.</p> <p>Creating a server requires several steps. First, you must create a request handler 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 and overriding 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; this method will process incoming requests. Second, you must instantiate one of the server classes, passing it the server’s address and the request handler class. Then call the <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> or <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 to process 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> to close the socket.</p> <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, you should explicitly declare how you want your threads to behave on an abrupt shutdown. 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 defines an attribute <em>daemon_threads</em>, which indicates whether or not the server should wait for thread termination. You should set the flag explicitly if you would like threads 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 that Python will not exit until all threads created by <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> have exited.</p> <p>Server classes have the same external methods and attributes, no matter what network protocol they use.</p> <div class="section" id="server-creation-notes"> <h2>20.17.1. Server Creation Notes<a class="headerlink" href="#server-creation-notes" title="Permalink to this headline">¶</a></h2> <p>There are five classes in an inheritance diagram, four of which represent synchronous servers of four types:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o">+------------+</span> <span class="o">|</span> <span class="n">BaseServer</span> <span class="o">|</span> <span class="o">+------------+</span> <span class="o">|</span> <span class="n">v</span> <span class="o">+-----------+</span> <span class="o">+------------------+</span> <span class="o">|</span> <span class="n">TCPServer</span> <span class="o">|------->|</span> <span class="n">UnixStreamServer</span> <span class="o">|</span> <span class="o">+-----------+</span> <span class="o">+------------------+</span> <span class="o">|</span> <span class="n">v</span> <span class="o">+-----------+</span> <span class="o">+--------------------+</span> <span class="o">|</span> <span class="n">UDPServer</span> <span class="o">|------->|</span> <span class="n">UnixDatagramServer</span> <span class="o">|</span> <span class="o">+-----------+</span> <span class="o">+--------------------+</span> </pre></div> </div> <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 from <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 Unix stream server is the address family, which is simply repeated in both Unix server classes.</p> <dl class="class"> <dt id="SocketServer.ForkingMixIn"> <em class="property">class </em><code class="descclassname">SocketServer.</code><code class="descname">ForkingMixIn</code><a class="headerlink" href="#SocketServer.ForkingMixIn" title="Permalink to this definition">¶</a></dt> <dt id="SocketServer.ThreadingMixIn"> <em class="property">class </em><code class="descclassname">SocketServer.</code><code class="descname">ThreadingMixIn</code><a class="headerlink" href="#SocketServer.ThreadingMixIn" title="Permalink to this definition">¶</a></dt> <dd><p>Forking and threading versions of each type of server can be created using 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> is created as follows:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="k">class</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> <span class="k">pass</span> </pre></div> </div> <p>The mix-in class comes first, since it overrides a method defined in <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 the behavior of the underlying server mechanism.</p> <p><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 the Forking classes mentioned below are only 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> </dd></dl> <dl class="class"> <dt id="SocketServer.ForkingTCPServer"> <em class="property">class </em><code class="descclassname">SocketServer.</code><code class="descname">ForkingTCPServer</code><a class="headerlink" href="#SocketServer.ForkingTCPServer" title="Permalink to this definition">¶</a></dt> <dt id="SocketServer.ForkingUDPServer"> <em class="property">class </em><code class="descclassname">SocketServer.</code><code class="descname">ForkingUDPServer</code><a class="headerlink" href="#SocketServer.ForkingUDPServer" title="Permalink to this definition">¶</a></dt> <dt id="SocketServer.ThreadingTCPServer"> <em class="property">class </em><code class="descclassname">SocketServer.</code><code class="descname">ThreadingTCPServer</code><a class="headerlink" href="#SocketServer.ThreadingTCPServer" title="Permalink to this definition">¶</a></dt> <dt id="SocketServer.ThreadingUDPServer"> <em class="property">class </em><code class="descclassname">SocketServer.</code><code class="descname">ThreadingUDPServer</code><a class="headerlink" href="#SocketServer.ThreadingUDPServer" title="Permalink to this definition">¶</a></dt> <dd><p>These classes are pre-defined using the mix-in classes.</p> </dd></dl> <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> and 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. You can then run various versions of the service by combining one of the server classes with your request handler class. The request handler class must be different for datagram or stream services. This can be hidden by using the handler subclasses <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> <p>Of course, you still have to use your head! For instance, it makes no sense to use a forking server if the service contains state in memory that can be modified by different requests, since the modifications in the child process would never reach the initial state kept in the parent process and passed to each child. In this case, you can use a threading server, but you will probably have to use locks to protect the integrity of the shared data.</p> <p>On the other hand, if you are building an HTTP server where all data is stored externally (for instance, in the file system), a synchronous class will essentially render the service “deaf” while one request is being handled – which may be for a very long time if a client is slow to receive all the data it has requested. Here a threading or forking server is appropriate.</p> <p>In some cases, it may be appropriate to process part of a request synchronously, but to finish processing in a forked child depending on the request data. This can be implemented by using a synchronous server and doing an explicit fork in the 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> <p>Another approach to handling multiple simultaneous requests in an environment that 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 too expensive or inappropriate for the service) is to maintain an explicit table of partially finished requests and to use <a class="reference internal" href="select.html#select.select" title="select.select"><code class="xref py py-func docutils literal notranslate"><span class="pre">select()</span></code></a> to decide which request to work on next (or whether to handle a new incoming request). This is particularly important for stream services where each client can potentially be connected for a long time (if threads or subprocesses cannot be used). See <a class="reference internal" href="asyncore.html#module-asyncore" title="asyncore: A base class for developing asynchronous socket handling services."><code class="xref py py-mod docutils literal notranslate"><span class="pre">asyncore</span></code></a> for another way to manage this.</p> </div> <div class="section" id="server-objects"> <h2>20.17.2. Server Objects<a class="headerlink" href="#server-objects" title="Permalink to this headline">¶</a></h2> <dl class="class"> <dt id="SocketServer.BaseServer"> <em class="property">class </em><code class="descclassname">SocketServer.</code><code class="descname">BaseServer</code><span class="sig-paren">(</span><em>server_address</em>, <em>RequestHandlerClass</em><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseServer" title="Permalink to this definition">¶</a></dt> <dd><p>This is the superclass of all Server objects in the module. It defines the interface, given below, but does not implement most of the methods, which is done in subclasses. The two parameters are stored in the respective <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> <dl class="method"> <dt id="SocketServer.BaseServer.fileno"> <code class="descname">fileno</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseServer.fileno" title="Permalink to this definition">¶</a></dt> <dd><p>Return an integer file descriptor for the socket on which the server is listening. This function is most commonly passed to <a class="reference internal" href="select.html#select.select" title="select.select"><code class="xref py py-func docutils literal notranslate"><span class="pre">select.select()</span></code></a>, to allow monitoring multiple servers in the same process.</p> </dd></dl> <dl class="method"> <dt id="SocketServer.BaseServer.handle_request"> <code class="descname">handle_request</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseServer.handle_request" title="Permalink to this definition">¶</a></dt> <dd><p>Process a single request. This function calls the following methods in order: <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>, and <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-provided <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 the handler 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> method will 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> seconds, <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 <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> will return.</p> </dd></dl> <dl class="method"> <dt id="SocketServer.BaseServer.serve_forever"> <code class="descname">serve_forever</code><span class="sig-paren">(</span><em>poll_interval=0.5</em><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseServer.serve_forever" title="Permalink to this definition">¶</a></dt> <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 for shutdown every <em>poll_interval</em> seconds. Ignores 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. If you need to do periodic tasks, do them in another thread.</p> </dd></dl> <dl class="method"> <dt id="SocketServer.BaseServer.shutdown"> <code class="descname">shutdown</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseServer.shutdown" title="Permalink to this definition">¶</a></dt> <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.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 2.6.</span></p> </div> </dd></dl> <dl class="method"> <dt id="SocketServer.BaseServer.server_close"> <code class="descname">server_close</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseServer.server_close" title="Permalink to this definition">¶</a></dt> <dd><p>Clean up the server. May be overridden.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 2.6.</span></p> </div> </dd></dl> <dl class="attribute"> <dt id="SocketServer.BaseServer.address_family"> <code class="descname">address_family</code><a class="headerlink" href="#SocketServer.BaseServer.address_family" title="Permalink to this definition">¶</a></dt> <dd><p>The family of protocols to which the server’s socket belongs. Common examples 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> and <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>.</p> </dd></dl> <dl class="attribute"> <dt id="SocketServer.BaseServer.RequestHandlerClass"> <code class="descname">RequestHandlerClass</code><a class="headerlink" href="#SocketServer.BaseServer.RequestHandlerClass" title="Permalink to this definition">¶</a></dt> <dd><p>The user-provided request handler class; an instance of this class is created for each request.</p> </dd></dl> <dl class="attribute"> <dt id="SocketServer.BaseServer.server_address"> <code class="descname">server_address</code><a class="headerlink" href="#SocketServer.BaseServer.server_address" title="Permalink to this definition">¶</a></dt> <dd><p>The address on which the server is listening. The format of addresses varies depending on the protocol family; see 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> module for details. For Internet protocols, this is a tuple containing a string giving the 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> </dd></dl> <dl class="attribute"> <dt id="SocketServer.BaseServer.socket"> <code class="descname">socket</code><a class="headerlink" href="#SocketServer.BaseServer.socket" title="Permalink to this definition">¶</a></dt> <dd><p>The socket object on which the server will listen for incoming requests.</p> </dd></dl> <p>The server classes support the following class variables:</p> <dl class="attribute"> <dt id="SocketServer.BaseServer.allow_reuse_address"> <code class="descname">allow_reuse_address</code><a class="headerlink" href="#SocketServer.BaseServer.allow_reuse_address" title="Permalink to this definition">¶</a></dt> <dd><p>Whether the server will allow the reuse of an address. This defaults to <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> </dd></dl> <dl class="attribute"> <dt id="SocketServer.BaseServer.request_queue_size"> <code class="descname">request_queue_size</code><a class="headerlink" href="#SocketServer.BaseServer.request_queue_size" title="Permalink to this definition">¶</a></dt> <dd><p>The size of the request queue. If it takes a long time to process a single request, any requests that arrive while the server is busy are placed into a queue, 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, further requests from clients will get a “Connection denied” error. The default value is usually 5, but this can be overridden by subclasses.</p> </dd></dl> <dl class="attribute"> <dt id="SocketServer.BaseServer.socket_type"> <code class="descname">socket_type</code><a class="headerlink" href="#SocketServer.BaseServer.socket_type" title="Permalink to this definition">¶</a></dt> <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> and <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> </dd></dl> <dl class="attribute"> <dt id="SocketServer.BaseServer.timeout"> <code class="descname">timeout</code><a class="headerlink" href="#SocketServer.BaseServer.timeout" title="Permalink to this definition">¶</a></dt> <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 is desired. 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 the timeout 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> </dd></dl> <p>There are various server methods that can be overridden by subclasses of base server 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 external users of the server object.</p> <dl class="method"> <dt id="SocketServer.BaseServer.finish_request"> <code class="descname">finish_request</code><span class="sig-paren">(</span><em>request</em>, <em>client_address</em><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseServer.finish_request" title="Permalink to this definition">¶</a></dt> <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> and calling 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> </dd></dl> <dl class="method"> <dt id="SocketServer.BaseServer.get_request"> <code class="descname">get_request</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseServer.get_request" title="Permalink to this definition">¶</a></dt> <dd><p>Must accept a request from the socket, and return a 2-tuple containing the <em>new</em> socket object to be used to communicate with the client, and the client’s address.</p> </dd></dl> <dl class="method"> <dt id="SocketServer.BaseServer.handle_error"> <code class="descname">handle_error</code><span class="sig-paren">(</span><em>request</em>, <em>client_address</em><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseServer.handle_error" title="Permalink to this definition">¶</a></dt> <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> method 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 raises an exception. The default action is to print the traceback to standard output and continue handling further requests.</p> </dd></dl> <dl class="method"> <dt id="SocketServer.BaseServer.handle_timeout"> <code class="descname">handle_timeout</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseServer.handle_timeout" title="Permalink to this definition">¶</a></dt> <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 a value 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 no requests being received. The default action for forking servers is to collect the status of any child processes that have exited, while in threading servers this method does nothing.</p> </dd></dl> <dl class="method"> <dt id="SocketServer.BaseServer.process_request"> <code class="descname">process_request</code><span class="sig-paren">(</span><em>request</em>, <em>client_address</em><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseServer.process_request" title="Permalink to this definition">¶</a></dt> <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 the <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 process or 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> 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> classes do this.</p> </dd></dl> <dl class="method"> <dt id="SocketServer.BaseServer.server_activate"> <code class="descname">server_activate</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseServer.server_activate" title="Permalink to this definition">¶</a></dt> <dd><p>Called by the server’s constructor to activate the server. The default behavior for 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> on the server’s socket. May be overridden.</p> </dd></dl> <dl class="method"> <dt id="SocketServer.BaseServer.server_bind"> <code class="descname">server_bind</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseServer.server_bind" title="Permalink to this definition">¶</a></dt> <dd><p>Called by the server’s constructor to bind the socket to the desired address. May be overridden.</p> </dd></dl> <dl class="method"> <dt id="SocketServer.BaseServer.verify_request"> <code class="descname">verify_request</code><span class="sig-paren">(</span><em>request</em>, <em>client_address</em><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseServer.verify_request" title="Permalink to this definition">¶</a></dt> <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 will be 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. This function can be overridden to implement access controls for a server. The default implementation always returns <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>.</p> </dd></dl> </dd></dl> </div> <div class="section" id="request-handler-objects"> <h2>20.17.3. Request Handler Objects<a class="headerlink" href="#request-handler-objects" title="Permalink to this headline">¶</a></h2> <dl class="class"> <dt id="SocketServer.BaseRequestHandler"> <em class="property">class </em><code class="descclassname">SocketServer.</code><code class="descname">BaseRequestHandler</code><a class="headerlink" href="#SocketServer.BaseRequestHandler" title="Permalink to this definition">¶</a></dt> <dd><p>This is the superclass of all request handler objects. It defines the interface, given below. A concrete request handler subclass must define 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 of the other methods. A new instance of the subclass is created for each request.</p> <dl class="method"> <dt id="SocketServer.BaseRequestHandler.setup"> <code class="descname">setup</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseRequestHandler.setup" title="Permalink to this definition">¶</a></dt> <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 actions required. The default implementation does nothing.</p> </dd></dl> <dl class="method"> <dt id="SocketServer.BaseRequestHandler.handle"> <code class="descname">handle</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseRequestHandler.handle" title="Permalink to this definition">¶</a></dt> <dd><p>This function must do all the work required to service a request. The default implementation does nothing. Several instance attributes are available to it; the request is available as <code class="xref py py-attr docutils literal notranslate"><span class="pre">self.request</span></code>; the client address as <code class="xref py py-attr docutils literal notranslate"><span class="pre">self.client_address</span></code>; and the server instance as <code class="xref py py-attr docutils literal notranslate"><span class="pre">self.server</span></code>, in case it needs access to per-server information.</p> <p>The type of <code class="xref py py-attr docutils literal notranslate"><span class="pre">self.request</span></code> is different for datagram or stream services. For stream services, <code class="xref py py-attr docutils literal notranslate"><span class="pre">self.request</span></code> is a socket object; for datagram services, <code class="xref py py-attr docutils literal notranslate"><span class="pre">self.request</span></code> is a pair of string and socket.</p> </dd></dl> <dl class="method"> <dt id="SocketServer.BaseRequestHandler.finish"> <code class="descname">finish</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#SocketServer.BaseRequestHandler.finish" title="Permalink to this definition">¶</a></dt> <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 actions required. 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> raises an exception, this function will not be called.</p> </dd></dl> </dd></dl> <dl class="class"> <dt id="SocketServer.StreamRequestHandler"> <em class="property">class </em><code class="descclassname">SocketServer.</code><code class="descname">StreamRequestHandler</code><a class="headerlink" href="#SocketServer.StreamRequestHandler" title="Permalink to this definition">¶</a></dt> <dt id="SocketServer.DatagramRequestHandler"> <em class="property">class </em><code class="descclassname">SocketServer.</code><code class="descname">DatagramRequestHandler</code><a class="headerlink" href="#SocketServer.DatagramRequestHandler" title="Permalink to this definition">¶</a></dt> <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 the <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> methods, and provide <code class="xref py py-attr docutils literal notranslate"><span class="pre">self.rfile</span></code> and <code class="xref py py-attr docutils literal notranslate"><span class="pre">self.wfile</span></code> attributes. The <code class="xref py py-attr docutils literal notranslate"><span class="pre">self.rfile</span></code> and <code class="xref py py-attr docutils literal notranslate"><span class="pre">self.wfile</span></code> attributes can be read or written, respectively, to get the request data or return data to the client.</p> </dd></dl> </div> <div class="section" id="examples"> <h2>20.17.4. Examples<a class="headerlink" href="#examples" title="Permalink to this headline">¶</a></h2> <div class="section" id="socketserver-tcpserver-example"> <h3>20.17.4.1. <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="Permalink to this headline">¶</a></h3> <p>This is the server side:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">SocketServer</span> <span class="k">class</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> <span class="sd">"""</span> <span class="sd"> The request handler class for our server.</span> <span class="sd"> It is instantiated once per connection to the server, and must</span> <span class="sd"> override the handle() method to implement communication to the</span> <span class="sd"> client.</span> <span class="sd"> """</span> <span class="k">def</span> <span class="nf">handle</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span> <span class="c1"># self.request is the TCP socket connected to the client</span> <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">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="o">.</span><span class="n">strip</span><span class="p">()</span> <span class="nb">print</span> <span class="s2">"</span><span class="si">{}</span><span class="s2"> wrote:"</span><span class="o">.</span><span class="n">format</span><span class="p">(</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="nb">print</span> <span class="bp">self</span><span class="o">.</span><span class="n">data</span> <span class="c1"># just send back the same data, but upper-cased</span> <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> <span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s2">"__main__"</span><span class="p">:</span> <span class="n">HOST</span><span class="p">,</span> <span class="n">PORT</span> <span class="o">=</span> <span class="s2">"localhost"</span><span class="p">,</span> <span class="mi">9999</span> <span class="c1"># Create the server, binding to localhost on port 9999</span> <span class="n">server</span> <span class="o">=</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="c1"># Activate the server; this will keep running until you</span> <span class="c1"># interrupt the program with Ctrl-C</span> <span class="n">server</span><span class="o">.</span><span class="n">serve_forever</span><span class="p">()</span> </pre></div> </div> <p>An alternative request handler class that makes use of streams (file-like objects that simplify communication by providing the standard file interface):</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="k">class</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> <span class="k">def</span> <span class="nf">handle</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span> <span class="c1"># self.rfile is a file-like object created by the handler;</span> <span class="c1"># we can now use e.g. readline() instead of raw recv() calls</span> <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="o">.</span><span class="n">strip</span><span class="p">()</span> <span class="nb">print</span> <span class="s2">"</span><span class="si">{}</span><span class="s2"> wrote:"</span><span class="o">.</span><span class="n">format</span><span class="p">(</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="nb">print</span> <span class="bp">self</span><span class="o">.</span><span class="n">data</span> <span class="c1"># Likewise, self.wfile is a file-like object used to write back</span> <span class="c1"># to the client</span> <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> </pre></div> </div> <p>The difference is that the <code class="docutils literal notranslate"><span class="pre">readline()</span></code> call in the second handler will call <code class="docutils literal notranslate"><span class="pre">recv()</span></code> multiple times until it encounters a newline character, while the single <code class="docutils literal notranslate"><span class="pre">recv()</span></code> call in the first handler will just return what has been sent from the client in one <code class="docutils literal notranslate"><span class="pre">sendall()</span></code> call.</p> <p>This is the client side:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">socket</span> <span class="kn">import</span> <span class="nn">sys</span> <span class="n">HOST</span><span class="p">,</span> <span class="n">PORT</span> <span class="o">=</span> <span class="s2">"localhost"</span><span class="p">,</span> <span class="mi">9999</span> <span class="n">data</span> <span class="o">=</span> <span class="s2">" "</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> <span class="c1"># Create a socket (SOCK_STREAM means a TCP socket)</span> <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_STREAM</span><span class="p">)</span> <span class="k">try</span><span class="p">:</span> <span class="c1"># Connect to server and send data</span> <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> <span class="n">sock</span><span class="o">.</span><span class="n">sendall</span><span class="p">(</span><span class="n">data</span> <span class="o">+</span> <span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">)</span> <span class="c1"># Receive data from the server and shut down</span> <span class="n">received</span> <span class="o">=</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="k">finally</span><span class="p">:</span> <span class="n">sock</span><span class="o">.</span><span class="n">close</span><span class="p">()</span> <span class="nb">print</span> <span class="s2">"Sent: </span><span class="si">{}</span><span class="s2">"</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">data</span><span class="p">)</span> <span class="nb">print</span> <span class="s2">"Received: </span><span class="si">{}</span><span class="s2">"</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">received</span><span class="p">)</span> </pre></div> </div> <p>The output of the example should look something like this:</p> <p>Server:</p> <div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$</span> python TCPServer.py <span class="go">127.0.0.1 wrote:</span> <span class="go">hello world with TCP</span> <span class="go">127.0.0.1 wrote:</span> <span class="go">python is nice</span> </pre></div> </div> <p>Client:</p> <div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$</span> python TCPClient.py hello world with TCP <span class="go">Sent: hello world with TCP</span> <span class="go">Received: HELLO WORLD WITH TCP</span> <span class="gp">$</span> python TCPClient.py python is nice <span class="go">Sent: python is nice</span> <span class="go">Received: PYTHON IS NICE</span> </pre></div> </div> </div> <div class="section" id="socketserver-udpserver-example"> <h3>20.17.4.2. <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="Permalink to this headline">¶</a></h3> <p>This is the server side:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">SocketServer</span> <span class="k">class</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> <span class="sd">"""</span> <span class="sd"> This class works similar to the TCP handler class, except that</span> <span class="sd"> self.request consists of a pair of data and client socket, and since</span> <span class="sd"> there is no connection the client address must be given explicitly</span> <span class="sd"> when sending data back via sendto().</span> <span class="sd"> """</span> <span class="k">def</span> <span class="nf">handle</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span> <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> <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> <span class="nb">print</span> <span class="s2">"</span><span class="si">{}</span><span class="s2"> wrote:"</span><span class="o">.</span><span class="n">format</span><span class="p">(</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="nb">print</span> <span class="n">data</span> <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> <span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s2">"__main__"</span><span class="p">:</span> <span class="n">HOST</span><span class="p">,</span> <span class="n">PORT</span> <span class="o">=</span> <span class="s2">"localhost"</span><span class="p">,</span> <span class="mi">9999</span> <span class="n">server</span> <span class="o">=</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="n">server</span><span class="o">.</span><span class="n">serve_forever</span><span class="p">()</span> </pre></div> </div> <p>This is the client side:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">socket</span> <span class="kn">import</span> <span class="nn">sys</span> <span class="n">HOST</span><span class="p">,</span> <span class="n">PORT</span> <span class="o">=</span> <span class="s2">"localhost"</span><span class="p">,</span> <span class="mi">9999</span> <span class="n">data</span> <span class="o">=</span> <span class="s2">" "</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> <span class="c1"># SOCK_DGRAM is the socket type to use for UDP sockets</span> <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> <span class="c1"># As you can see, there is no connect() call; UDP has no connections.</span> <span class="c1"># Instead, data is directly sent to the recipient via sendto().</span> <span class="n">sock</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="s2">"</span><span class="se">\n</span><span class="s2">"</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> <span class="n">received</span> <span class="o">=</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="nb">print</span> <span class="s2">"Sent: </span><span class="si">{}</span><span class="s2">"</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">data</span><span class="p">)</span> <span class="nb">print</span> <span class="s2">"Received: </span><span class="si">{}</span><span class="s2">"</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">received</span><span class="p">)</span> </pre></div> </div> <p>The output of the example should look exactly like for the TCP server example.</p> </div> <div class="section" id="asynchronous-mixins"> <h3>20.17.4.3. Asynchronous Mixins<a class="headerlink" href="#asynchronous-mixins" title="Permalink to this headline">¶</a></h3> <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> and <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> <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> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">socket</span> <span class="kn">import</span> <span class="nn">threading</span> <span class="kn">import</span> <span class="nn">SocketServer</span> <span class="k">class</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> <span class="k">def</span> <span class="nf">handle</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span> <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="o">.</span><span class="n">recv</span><span class="p">(</span><span class="mi">1024</span><span class="p">)</span> <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> <span class="n">response</span> <span class="o">=</span> <span class="s2">"</span><span class="si">{}</span><span class="s2">: </span><span class="si">{}</span><span class="s2">"</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="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> <span class="k">class</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> <span class="k">pass</span> <span class="k">def</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> <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_STREAM</span><span class="p">)</span> <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> <span class="k">try</span><span class="p">:</span> <span class="n">sock</span><span class="o">.</span><span class="n">sendall</span><span class="p">(</span><span class="n">message</span><span class="p">)</span> <span class="n">response</span> <span class="o">=</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="nb">print</span> <span class="s2">"Received: </span><span class="si">{}</span><span class="s2">"</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">response</span><span class="p">)</span> <span class="k">finally</span><span class="p">:</span> <span class="n">sock</span><span class="o">.</span><span class="n">close</span><span class="p">()</span> <span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s2">"__main__"</span><span class="p">:</span> <span class="c1"># Port 0 means to select an arbitrary unused port</span> <span class="n">HOST</span><span class="p">,</span> <span class="n">PORT</span> <span class="o">=</span> <span class="s2">"localhost"</span><span class="p">,</span> <span class="mi">0</span> <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> <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> <span class="c1"># Start a thread with the server -- that thread will then start one</span> <span class="c1"># more thread for each request</span> <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> <span class="c1"># Exit the server thread when the main thread terminates</span> <span class="n">server_thread</span><span class="o">.</span><span class="n">daemon</span> <span class="o">=</span> <span class="kc">True</span> <span class="n">server_thread</span><span class="o">.</span><span class="n">start</span><span class="p">()</span> <span class="nb">print</span> <span class="s2">"Server loop running in thread:"</span><span class="p">,</span> <span class="n">server_thread</span><span class="o">.</span><span class="n">name</span> <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">"Hello World 1"</span><span class="p">)</span> <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">"Hello World 2"</span><span class="p">)</span> <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">"Hello World 3"</span><span class="p">)</span> <span class="n">server</span><span class="o">.</span><span class="n">shutdown</span><span class="p">()</span> <span class="n">server</span><span class="o">.</span><span class="n">server_close</span><span class="p">()</span> </pre></div> </div> <p>The output of the example should look something like this:</p> <div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$</span> python ThreadedTCPServer.py <span class="go">Server loop running in thread: Thread-1</span> <span class="go">Received: Thread-2: Hello World 1</span> <span class="go">Received: Thread-3: Hello World 2</span> <span class="go">Received: Thread-4: Hello World 3</span> </pre></div> </div> <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 server will spawn a new process for each request. Available 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> </div> </div> </div> </div> </div> </div> <div class="sphinxsidebar" role="navigation" aria-label="main navigation"> <div class="sphinxsidebarwrapper"> <h3><a href="../contents.html">Table Of Contents</a></h3> <ul> <li><a class="reference internal" href="#">20.17. <code class="docutils literal notranslate"><span class="pre">SocketServer</span></code> — A framework for network servers</a><ul> <li><a class="reference internal" href="#server-creation-notes">20.17.1. Server Creation Notes</a></li> <li><a class="reference internal" href="#server-objects">20.17.2. Server Objects</a></li> <li><a class="reference internal" href="#request-handler-objects">20.17.3. Request Handler Objects</a></li> <li><a class="reference internal" href="#examples">20.17.4. Examples</a><ul> <li><a class="reference internal" href="#socketserver-tcpserver-example">20.17.4.1. <code class="docutils literal notranslate"><span class="pre">SocketServer.TCPServer</span></code> Example</a></li> <li><a class="reference internal" href="#socketserver-udpserver-example">20.17.4.2. <code class="docutils literal notranslate"><span class="pre">SocketServer.UDPServer</span></code> Example</a></li> <li><a class="reference internal" href="#asynchronous-mixins">20.17.4.3. Asynchronous Mixins</a></li> </ul> </li> </ul> </li> </ul> <h4>Previous topic</h4> <p class="topless"><a href="urlparse.html" title="previous chapter">20.16. <code class="docutils literal notranslate"><span class="pre">urlparse</span></code> — Parse URLs into components</a></p> <h4>Next topic</h4> <p class="topless"><a href="basehttpserver.html" title="next chapter">20.18. <code class="docutils literal notranslate"><span class="pre">BaseHTTPServer</span></code> — Basic HTTP server</a></p> <div role="note" aria-label="source link"> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../_sources/library/socketserver.rst.txt" rel="nofollow">Show Source</a></li> </ul> </div> <div id="searchbox" style="display: none" role="search"> <h3>Quick search</h3> <div class="searchformwrapper"> <form class="search" action="../search.html" method="get"> <input type="text" name="q" /> <input type="submit" value="Go" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> </div> </div> <script type="text/javascript">$('#searchbox').show(0);</script> </div> </div> <div class="clearer"></div> </div> <div class="related" role="navigation" aria-label="related navigation"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" >index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="basehttpserver.html" title="20.18. 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