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<h3><a href="../contents.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">asynchat – Asynchronous protocol handler</a><ul>
<li><a class="reference internal" href="#message-terminators">Message Terminators</a></li>
<li><a class="reference internal" href="#server-and-handler">Server and Handler</a></li>
<li><a class="reference internal" href="#client">Client</a></li>
<li><a class="reference internal" href="#putting-it-all-together">Putting It All Together</a></li>
</ul>
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<div class="section" id="module-asynchat">
<span id="asynchat-asynchronous-protocol-handler"></span><h1>asynchat – Asynchronous protocol handler<a class="headerlink" href="#module-asynchat" title="Permalink to this headline">¶</a></h1>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Purpose:</th><td class="field-body">Asynchronous network communication protocol handler</td>
</tr>
<tr class="field"><th class="field-name">Python Version:</th><td class="field-body">1.5.2 and later</td>
</tr>
</tbody>
</table>
<p>The <a class="reference internal" href="#module-asynchat" title="asynchat: Asynchronous protocol handler"><tt class="xref py py-mod docutils literal"><span class="pre">asynchat</span></tt></a> module builds on <a class="reference internal" href="../asyncore/index.html#module-asyncore" title="asyncore: Asynchronous I/O handler"><tt class="xref py py-mod docutils literal"><span class="pre">asyncore</span></tt></a> to make it easier
to implement protocols based on passing messages back and forth
between server and client. The <tt class="xref py py-class docutils literal"><span class="pre">async_chat</span></tt> class is an
<tt class="xref py py-class docutils literal"><span class="pre">asyncore.dispatcher</span></tt> subclass that receives data and looks for
a message terminator. Your subclass only needs to specify what to do
when data comes in and how to respond once the terminator is
found. Outgoing data is queued for transmission via FIFO objects
managed by <tt class="xref py py-class docutils literal"><span class="pre">async_chat</span></tt>.</p>
<div class="section" id="message-terminators">
<h2>Message Terminators<a class="headerlink" href="#message-terminators" title="Permalink to this headline">¶</a></h2>
<p>Incoming messages are broken up based on <em>terminators</em>, controlled for
each instance via <tt class="xref py py-func docutils literal"><span class="pre">set_terminator()</span></tt>. There are three possible
configurations:</p>
<ol class="arabic simple">
<li>If a string argument is passed to <tt class="xref py py-func docutils literal"><span class="pre">set_terminator()</span></tt>, the
message is considered complete when that string appears in the
input data.</li>
<li>If a numeric argument is passed, the message is considered complete
when that many bytes have been read.</li>
<li>If <tt class="xref docutils literal"><span class="pre">None</span></tt> is passed, message termination is not managed by
<tt class="xref py py-class docutils literal"><span class="pre">async_chat</span></tt>.</li>
</ol>
<p>The <tt class="xref py py-class docutils literal"><span class="pre">EchoServer</span></tt> example below uses both a simple string
terminator and a message length terminator, depending on the context
of the incoming data. The HTTP request handler example in the standard
library documentation offers another example of how to change the
terminator based on the context to differentiate between HTTP headers
and the HTTP POST request body.</p>
</div>
<div class="section" id="server-and-handler">
<h2>Server and Handler<a class="headerlink" href="#server-and-handler" title="Permalink to this headline">¶</a></h2>
<p>To make it easier to understand how <a class="reference internal" href="#module-asynchat" title="asynchat: Asynchronous protocol handler"><tt class="xref py py-mod docutils literal"><span class="pre">asynchat</span></tt></a> is different from
<a class="reference internal" href="../asyncore/index.html#module-asyncore" title="asyncore: Asynchronous I/O handler"><tt class="xref py py-mod docutils literal"><span class="pre">asyncore</span></tt></a>, the examples here duplicate the functionality of the
<tt class="xref py py-class docutils literal"><span class="pre">EchoServer</span></tt> example from the <a class="reference internal" href="../asyncore/index.html#module-asyncore" title="asyncore: Asynchronous I/O handler"><tt class="xref py py-mod docutils literal"><span class="pre">asyncore</span></tt></a> discussion. The
same pieces are needed: a server object to accept connections, handler
objects to deal with communication with each client, and client
objects to initiate the conversation.</p>
<p>The <tt class="xref py py-class docutils literal"><span class="pre">EchoServer</span></tt> needed to work with <a class="reference internal" href="#module-asynchat" title="asynchat: Asynchronous protocol handler"><tt class="xref py py-mod docutils literal"><span class="pre">asynchat</span></tt></a> is
essentially the same as the one created for the <a class="reference internal" href="../asyncore/index.html#module-asyncore" title="asyncore: Asynchronous I/O handler"><tt class="xref py py-mod docutils literal"><span class="pre">asyncore</span></tt></a>
example, with fewer <a class="reference internal" href="../logging/index.html#module-logging" title="logging: Report status, error, and informational messages."><tt class="xref py py-mod docutils literal"><span class="pre">logging</span></tt></a> calls because they are less
interesting this time around:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">asyncore</span>
<span class="kn">import</span> <span class="nn">logging</span>
<span class="kn">import</span> <span class="nn">socket</span>
<span class="kn">from</span> <span class="nn">asynchat_echo_handler</span> <span class="kn">import</span> <span class="n">EchoHandler</span>
<span class="k">class</span> <span class="nc">EchoServer</span><span class="p">(</span><span class="n">asyncore</span><span class="o">.</span><span class="n">dispatcher</span><span class="p">):</span>
<span class="sd">"""Receives connections and establishes handlers for each client.</span>
<span class="sd"> """</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">address</span><span class="p">):</span>
<span class="n">asyncore</span><span class="o">.</span><span class="n">dispatcher</span><span class="o">.</span><span class="n">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">create_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="bp">self</span><span class="o">.</span><span class="n">bind</span><span class="p">(</span><span class="n">address</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">address</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">socket</span><span class="o">.</span><span class="n">getsockname</span><span class="p">()</span>
<span class="bp">self</span><span class="o">.</span><span class="n">listen</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="k">return</span>
<span class="k">def</span> <span class="nf">handle_accept</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="c"># Called when a client connects to our socket</span>
<span class="n">client_info</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">accept</span><span class="p">()</span>
<span class="n">EchoHandler</span><span class="p">(</span><span class="n">sock</span><span class="o">=</span><span class="n">client_info</span><span class="p">[</span><span class="mi">0</span><span class="p">])</span>
<span class="c"># We only want to deal with one client at a time,</span>
<span class="c"># so close as soon as we set up the handler.</span>
<span class="c"># Normally you would not do this and the server</span>
<span class="c"># would run forever or until it received instructions</span>
<span class="c"># to stop.</span>
<span class="bp">self</span><span class="o">.</span><span class="n">handle_close</span><span class="p">()</span>
<span class="k">return</span>
<span class="k">def</span> <span class="nf">handle_close</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</pre></div>
</div>
<p>The <tt class="xref py py-class docutils literal"><span class="pre">EchoHandler</span></tt> is based on <tt class="docutils literal"><span class="pre">asynchat.async_chat</span></tt> instead
of the <tt class="xref py py-class docutils literal"><span class="pre">asyncore.dispatcher</span></tt> this time around. It operates at a
slightly higher level of abstraction, so reading and writing are
handled automatically. The buffer needs to know four things:</p>
<ul class="simple">
<li>what to do with incoming data (by overriding
<tt class="xref py py-func docutils literal"><span class="pre">handle_incoming_data()</span></tt>)</li>
<li>how to recognize the end of an incoming message (via
<tt class="xref py py-func docutils literal"><span class="pre">set_terminator()</span></tt>)</li>
<li>what to do when a complete message is received (in
<tt class="xref py py-func docutils literal"><span class="pre">found_terminator()</span></tt>)</li>
<li>what data to send (using <tt class="xref py py-func docutils literal"><span class="pre">push()</span></tt>)</li>
</ul>
<p>The example application has two operating modes. It is either waiting
for a command of the form <tt class="docutils literal"><span class="pre">ECHO</span> <span class="pre">length\n</span></tt>, or waiting for the data
to be echoed. The mode is toggled back and forth by setting an
instance variable <em>process_data</em> to the method to be invoked when the
terminator is found and then changing the terminator as appropriate.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">asynchat</span>
<span class="kn">import</span> <span class="nn">logging</span>
<span class="k">class</span> <span class="nc">EchoHandler</span><span class="p">(</span><span class="n">asynchat</span><span class="o">.</span><span class="n">async_chat</span><span class="p">):</span>
<span class="sd">"""Handles echoing messages from a single client.</span>
<span class="sd"> """</span>
<span class="c"># Artificially reduce buffer sizes to illustrate</span>
<span class="c"># sending and receiving partial messages.</span>
<span class="n">ac_in_buffer_size</span> <span class="o">=</span> <span class="mi">64</span>
<span class="n">ac_out_buffer_size</span> <span class="o">=</span> <span class="mi">64</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">sock</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">received_data</span> <span class="o">=</span> <span class="p">[]</span>
<span class="bp">self</span><span class="o">.</span><span class="n">logger</span> <span class="o">=</span> <span class="n">logging</span><span class="o">.</span><span class="n">getLogger</span><span class="p">(</span><span class="s">'EchoHandler'</span><span class="p">)</span>
<span class="n">asynchat</span><span class="o">.</span><span class="n">async_chat</span><span class="o">.</span><span class="n">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">sock</span><span class="p">)</span>
<span class="c"># Start looking for the ECHO command</span>
<span class="bp">self</span><span class="o">.</span><span class="n">process_data</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">_process_command</span>
<span class="bp">self</span><span class="o">.</span><span class="n">set_terminator</span><span class="p">(</span><span class="s">'</span><span class="se">\n</span><span class="s">'</span><span class="p">)</span>
<span class="k">return</span>
<span class="k">def</span> <span class="nf">collect_incoming_data</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">data</span><span class="p">):</span>
<span class="sd">"""Read an incoming message from the client and put it into our outgoing queue."""</span>
<span class="bp">self</span><span class="o">.</span><span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s">'collect_incoming_data() -> (</span><span class="si">%d</span><span class="s"> bytes)</span><span class="se">\n</span><span class="s">"""</span><span class="si">%s</span><span class="s">"""'</span><span class="p">,</span> <span class="nb">len</span><span class="p">(</span><span class="n">data</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">received_data</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">found_terminator</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="sd">"""The end of a command or message has been seen."""</span>
<span class="bp">self</span><span class="o">.</span><span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s">'found_terminator()'</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">process_data</span><span class="p">()</span>
<span class="k">def</span> <span class="nf">_process_command</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="sd">"""We have the full ECHO command"""</span>
<span class="n">command</span> <span class="o">=</span> <span class="s">''</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">received_data</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s">'_process_command() "</span><span class="si">%s</span><span class="s">"'</span><span class="p">,</span> <span class="n">command</span><span class="p">)</span>
<span class="n">command_verb</span><span class="p">,</span> <span class="n">command_arg</span> <span class="o">=</span> <span class="n">command</span><span class="o">.</span><span class="n">strip</span><span class="p">()</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="s">' '</span><span class="p">)</span>
<span class="n">expected_data_len</span> <span class="o">=</span> <span class="nb">int</span><span class="p">(</span><span class="n">command_arg</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">set_terminator</span><span class="p">(</span><span class="n">expected_data_len</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">process_data</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">_process_message</span>
<span class="bp">self</span><span class="o">.</span><span class="n">received_data</span> <span class="o">=</span> <span class="p">[]</span>
<span class="k">def</span> <span class="nf">_process_message</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="sd">"""We have read the entire message to be sent back to the client"""</span>
<span class="n">to_echo</span> <span class="o">=</span> <span class="s">''</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">received_data</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s">'_process_message() echoing</span><span class="se">\n</span><span class="s">"""</span><span class="si">%s</span><span class="s">"""'</span><span class="p">,</span> <span class="n">to_echo</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="n">to_echo</span><span class="p">)</span>
<span class="c"># Disconnect after sending the entire response</span>
<span class="c"># since we only want to do one thing at a time</span>
<span class="bp">self</span><span class="o">.</span><span class="n">close_when_done</span><span class="p">()</span>
</pre></div>
</div>
<p>Once the complete command is found, the handler switches to
message-processing mode and waits for the complete set of text to be
received. When all of the data is available, it is pushed onto the
outgoing channel and set up the handler to be closed once the data is
sent.</p>
</div>
<div class="section" id="client">
<h2>Client<a class="headerlink" href="#client" title="Permalink to this headline">¶</a></h2>
<p>The client works in much the same way as the handler. As with the
<a class="reference internal" href="../asyncore/index.html#module-asyncore" title="asyncore: Asynchronous I/O handler"><tt class="xref py py-mod docutils literal"><span class="pre">asyncore</span></tt></a> implementation, the message to be sent is an argument
to the client’s constructor. When the socket connection is
established, <tt class="xref py py-func docutils literal"><span class="pre">handle_connect()</span></tt> is called so the client can send
the command and message data.</p>
<p>The command is pushed directly, but a special “producer” class is used
for the message text. The producer is polled for chunks of data to
send out over the network. When the producer returns an empty string,
it is assumed to be empty and writing stops.</p>
<p>The client expects just the message data in response, so it sets an
integer terminator and collects data in a list until the entire
message has been received.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">asynchat</span>
<span class="kn">import</span> <span class="nn">logging</span>
<span class="kn">import</span> <span class="nn">socket</span>
<span class="k">class</span> <span class="nc">EchoClient</span><span class="p">(</span><span class="n">asynchat</span><span class="o">.</span><span class="n">async_chat</span><span class="p">):</span>
<span class="sd">"""Sends messages to the server and receives responses.</span>
<span class="sd"> """</span>
<span class="c"># Artificially reduce buffer sizes to illustrate</span>
<span class="c"># sending and receiving partial messages.</span>
<span class="n">ac_in_buffer_size</span> <span class="o">=</span> <span class="mi">64</span>
<span class="n">ac_out_buffer_size</span> <span class="o">=</span> <span class="mi">64</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</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">message</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">message</span> <span class="o">=</span> <span class="n">message</span>
<span class="bp">self</span><span class="o">.</span><span class="n">received_data</span> <span class="o">=</span> <span class="p">[]</span>
<span class="bp">self</span><span class="o">.</span><span class="n">logger</span> <span class="o">=</span> <span class="n">logging</span><span class="o">.</span><span class="n">getLogger</span><span class="p">(</span><span class="s">'EchoClient'</span><span class="p">)</span>
<span class="n">asynchat</span><span class="o">.</span><span class="n">async_chat</span><span class="o">.</span><span class="n">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">create_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="bp">self</span><span class="o">.</span><span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s">'connecting to </span><span class="si">%s</span><span class="s">'</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="bp">self</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="k">return</span>
<span class="k">def</span> <span class="nf">handle_connect</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s">'handle_connect()'</span><span class="p">)</span>
<span class="c"># Send the command</span>
<span class="bp">self</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="s">'ECHO </span><span class="si">%d</span><span class="se">\n</span><span class="s">'</span> <span class="o">%</span> <span class="nb">len</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">message</span><span class="p">))</span>
<span class="c"># Send the data</span>
<span class="bp">self</span><span class="o">.</span><span class="n">push_with_producer</span><span class="p">(</span><span class="n">EchoProducer</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">message</span><span class="p">,</span> <span class="n">buffer_size</span><span class="o">=</span><span class="bp">self</span><span class="o">.</span><span class="n">ac_out_buffer_size</span><span class="p">))</span>
<span class="c"># We expect the data to come back as-is, </span>
<span class="c"># so set a length-based terminator</span>
<span class="bp">self</span><span class="o">.</span><span class="n">set_terminator</span><span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">message</span><span class="p">))</span>
<span class="k">def</span> <span class="nf">collect_incoming_data</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">data</span><span class="p">):</span>
<span class="sd">"""Read an incoming message from the client and put it into our outgoing queue."""</span>
<span class="bp">self</span><span class="o">.</span><span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s">'collect_incoming_data() -> (</span><span class="si">%d</span><span class="s">)</span><span class="se">\n</span><span class="s">"""</span><span class="si">%s</span><span class="s">"""'</span><span class="p">,</span> <span class="nb">len</span><span class="p">(</span><span class="n">data</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">received_data</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">found_terminator</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s">'found_terminator()'</span><span class="p">)</span>
<span class="n">received_message</span> <span class="o">=</span> <span class="s">''</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">received_data</span><span class="p">)</span>
<span class="k">if</span> <span class="n">received_message</span> <span class="o">==</span> <span class="bp">self</span><span class="o">.</span><span class="n">message</span><span class="p">:</span>
<span class="bp">self</span><span class="o">.</span><span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s">'RECEIVED COPY OF MESSAGE'</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="bp">self</span><span class="o">.</span><span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s">'ERROR IN TRANSMISSION'</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s">'EXPECTED "</span><span class="si">%s</span><span class="s">"'</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">message</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s">'RECEIVED "</span><span class="si">%s</span><span class="s">"'</span><span class="p">,</span> <span class="n">received_message</span><span class="p">)</span>
<span class="k">return</span>
<span class="k">class</span> <span class="nc">EchoProducer</span><span class="p">(</span><span class="n">asynchat</span><span class="o">.</span><span class="n">simple_producer</span><span class="p">):</span>
<span class="n">logger</span> <span class="o">=</span> <span class="n">logging</span><span class="o">.</span><span class="n">getLogger</span><span class="p">(</span><span class="s">'EchoProducer'</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">more</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="n">response</span> <span class="o">=</span> <span class="n">asynchat</span><span class="o">.</span><span class="n">simple_producer</span><span class="o">.</span><span class="n">more</span><span class="p">(</span><span class="bp">self</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s">'more() -> (</span><span class="si">%s</span><span class="s"> bytes)</span><span class="se">\n</span><span class="s">"""</span><span class="si">%s</span><span class="s">"""'</span><span class="p">,</span> <span class="nb">len</span><span class="p">(</span><span class="n">response</span><span class="p">),</span> <span class="n">response</span><span class="p">)</span>
<span class="k">return</span> <span class="n">response</span>
</pre></div>
</div>
</div>
<div class="section" id="putting-it-all-together">
<h2>Putting It All Together<a class="headerlink" href="#putting-it-all-together" title="Permalink to this headline">¶</a></h2>
<p>The main program for this example sets up the client and server in the
same <a class="reference internal" href="../asyncore/index.html#module-asyncore" title="asyncore: Asynchronous I/O handler"><tt class="xref py py-mod docutils literal"><span class="pre">asyncore</span></tt></a> main loop.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">asyncore</span>
<span class="kn">import</span> <span class="nn">logging</span>
<span class="kn">import</span> <span class="nn">socket</span>
<span class="kn">from</span> <span class="nn">asynchat_echo_server</span> <span class="kn">import</span> <span class="n">EchoServer</span>
<span class="kn">from</span> <span class="nn">asynchat_echo_client</span> <span class="kn">import</span> <span class="n">EchoClient</span>
<span class="n">logging</span><span class="o">.</span><span class="n">basicConfig</span><span class="p">(</span><span class="n">level</span><span class="o">=</span><span class="n">logging</span><span class="o">.</span><span class="n">DEBUG</span><span class="p">,</span>
<span class="n">format</span><span class="o">=</span><span class="s">'</span><span class="si">%(name)s</span><span class="s">: </span><span class="si">%(message)s</span><span class="s">'</span><span class="p">,</span>
<span class="p">)</span>
<span class="n">address</span> <span class="o">=</span> <span class="p">(</span><span class="s">'localhost'</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span> <span class="c"># let the kernel give us a port</span>
<span class="n">server</span> <span class="o">=</span> <span class="n">EchoServer</span><span class="p">(</span><span class="n">address</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">address</span> <span class="c"># find out what port we were given</span>
<span class="n">message_data</span> <span class="o">=</span> <span class="nb">open</span><span class="p">(</span><span class="s">'lorem.txt'</span><span class="p">,</span> <span class="s">'r'</span><span class="p">)</span><span class="o">.</span><span class="n">read</span><span class="p">()</span>
<span class="n">client</span> <span class="o">=</span> <span class="n">EchoClient</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="o">=</span><span class="n">message_data</span><span class="p">)</span>
<span class="n">asyncore</span><span class="o">.</span><span class="n">loop</span><span class="p">()</span>
</pre></div>
</div>
<p>Normally you would have them in separate processes, but this makes it
easier to show the combined output.</p>
<div class="highlight-python"><pre>$ python asynchat_echo_main.py
EchoClient: connecting to ('127.0.0.1', 54380)
EchoClient: handle_connect()
EchoProducer: more() -> (64 bytes)
"""Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Donec
"""
EchoProducer: more() -> (64 bytes)
"""egestas, enim et consectetuer ullamcorper, lectus ligula rutrum """
EchoProducer: more() -> (38 bytes)
"""leo, a
elementum elit tortor eu quam.
"""
EchoHandler: collect_incoming_data() -> (8 bytes)
"""ECHO 166"""
EchoHandler: found_terminator()
EchoHandler: _process_command() "ECHO 166"
EchoHandler: collect_incoming_data() -> (55 bytes)
"""Lorem ipsum dolor sit amet, consectetuer adipiscing eli"""
EchoProducer: more() -> (0 bytes)
""""""
EchoHandler: collect_incoming_data() -> (64 bytes)
"""t. Donec
egestas, enim et consectetuer ullamcorper, lectus ligul"""
EchoHandler: collect_incoming_data() -> (47 bytes)
"""a rutrum leo, a
elementum elit tortor eu quam.
"""
EchoHandler: found_terminator()
EchoHandler: _process_message() echoing
"""Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Donec
egestas, enim et consectetuer ullamcorper, lectus ligula rutrum leo, a
elementum elit tortor eu quam.
"""
EchoClient: collect_incoming_data() -> (64)
"""Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Donec
"""
EchoClient: collect_incoming_data() -> (64)
"""egestas, enim et consectetuer ullamcorper, lectus ligula rutrum """
EchoClient: collect_incoming_data() -> (38)
"""leo, a
elementum elit tortor eu quam.
"""
EchoClient: found_terminator()
EchoClient: RECEIVED COPY OF MESSAGE</pre>
</div>
<div class="admonition-see-also admonition seealso">
<p class="first admonition-title">See also</p>
<dl class="last docutils">
<dt><a class="reference external" href="http://docs.python.org/library/asynchat.html">asynchat</a></dt>
<dd>The standard library documentation for this module.</dd>
<dt><a class="reference internal" href="../asyncore/index.html#module-asyncore" title="asyncore: Asynchronous I/O handler"><tt class="xref py py-mod docutils literal"><span class="pre">asyncore</span></tt></a></dt>
<dd>The asyncore module implements an lower-level asynchronous I/O
event loop.</dd>
</dl>
</div>
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