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<section id="timer-file-descriptor-howto">
<span id="timerfd-howto"></span><h1>timer file descriptor HOWTO<a class="headerlink" href="#timer-file-descriptor-howto" title="Link to this heading">¶</a></h1>
<dl class="field-list simple">
<dt class="field-odd">Release<span class="colon">:</span></dt>
<dd class="field-odd"><p>1.13</p>
</dd>
</dl>
<p>This HOWTO discusses Python’s support for the linux timer file descriptor.</p>
<section id="examples">
<h2>Examples<a class="headerlink" href="#examples" title="Link to this heading">¶</a></h2>
<p>The following example shows how to use a timer file descriptor
to execute a function twice a second:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="c1"># Practical scripts should use really use a non-blocking timer,</span>
<span class="c1"># we use a blocking timer here for simplicity.</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">os</span><span class="o">,</span><span class="w"> </span><span class="nn">time</span>
<span class="c1"># Create the timer file descriptor</span>
<span class="n">fd</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">timerfd_create</span><span class="p">(</span><span class="n">time</span><span class="o">.</span><span class="n">CLOCK_REALTIME</span><span class="p">)</span>
<span class="c1"># Start the timer in 1 second, with an interval of half a second</span>
<span class="n">os</span><span class="o">.</span><span class="n">timerfd_settime</span><span class="p">(</span><span class="n">fd</span><span class="p">,</span> <span class="n">initial</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span> <span class="n">interval</span><span class="o">=</span><span class="mf">0.5</span><span class="p">)</span>
<span class="k">try</span><span class="p">:</span>
<span class="c1"># Process timer events four times.</span>
<span class="k">for</span> <span class="n">_</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">4</span><span class="p">):</span>
<span class="c1"># read() will block until the timer expires</span>
<span class="n">_</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">read</span><span class="p">(</span><span class="n">fd</span><span class="p">,</span> <span class="mi">8</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="s2">"Timer expired"</span><span class="p">)</span>
<span class="k">finally</span><span class="p">:</span>
<span class="c1"># Remember to close the timer file descriptor!</span>
<span class="n">os</span><span class="o">.</span><span class="n">close</span><span class="p">(</span><span class="n">fd</span><span class="p">)</span>
</pre></div>
</div>
<p>To avoid the precision loss caused by the <a class="reference internal" href="../library/functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a> type,
timer file descriptors allow specifying initial expiration and interval
in integer nanoseconds with <code class="docutils literal notranslate"><span class="pre">_ns</span></code> variants of the functions.</p>
<p>This example shows how <a class="reference internal" href="../library/select.html#select.epoll" title="select.epoll"><code class="xref py py-func docutils literal notranslate"><span class="pre">epoll()</span></code></a> can be used with timer file
descriptors to wait until the file descriptor is ready for reading:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">os</span><span class="o">,</span><span class="w"> </span><span class="nn">time</span><span class="o">,</span><span class="w"> </span><span class="nn">select</span><span class="o">,</span><span class="w"> </span><span class="nn">socket</span><span class="o">,</span><span class="w"> </span><span class="nn">sys</span>
<span class="c1"># Create an epoll object</span>
<span class="n">ep</span> <span class="o">=</span> <span class="n">select</span><span class="o">.</span><span class="n">epoll</span><span class="p">()</span>
<span class="c1"># In this example, use loopback address to send "stop" command to the server.</span>
<span class="c1">#</span>
<span class="c1"># $ telnet 127.0.0.1 1234</span>
<span class="c1"># Trying 127.0.0.1...</span>
<span class="c1"># Connected to 127.0.0.1.</span>
<span class="c1"># Escape character is '^]'.</span>
<span class="c1"># stop</span>
<span class="c1"># Connection closed by foreign host.</span>
<span class="c1">#</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">bind</span><span class="p">((</span><span class="s2">"127.0.0.1"</span><span class="p">,</span> <span class="mi">1234</span><span class="p">))</span>
<span class="n">sock</span><span class="o">.</span><span class="n">setblocking</span><span class="p">(</span><span class="kc">False</span><span class="p">)</span>
<span class="n">sock</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="n">ep</span><span class="o">.</span><span class="n">register</span><span class="p">(</span><span class="n">sock</span><span class="p">,</span> <span class="n">select</span><span class="o">.</span><span class="n">EPOLLIN</span><span class="p">)</span>
<span class="c1"># Create timer file descriptors in non-blocking mode.</span>
<span class="n">num</span> <span class="o">=</span> <span class="mi">3</span>
<span class="n">fds</span> <span class="o">=</span> <span class="p">[]</span>
<span class="k">for</span> <span class="n">_</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">num</span><span class="p">):</span>
<span class="n">fd</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">timerfd_create</span><span class="p">(</span><span class="n">time</span><span class="o">.</span><span class="n">CLOCK_REALTIME</span><span class="p">,</span> <span class="n">flags</span><span class="o">=</span><span class="n">os</span><span class="o">.</span><span class="n">TFD_NONBLOCK</span><span class="p">)</span>
<span class="n">fds</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">fd</span><span class="p">)</span>
<span class="c1"># Register the timer file descriptor for read events</span>
<span class="n">ep</span><span class="o">.</span><span class="n">register</span><span class="p">(</span><span class="n">fd</span><span class="p">,</span> <span class="n">select</span><span class="o">.</span><span class="n">EPOLLIN</span><span class="p">)</span>
<span class="c1"># Start the timer with os.timerfd_settime_ns() in nanoseconds.</span>
<span class="c1"># Timer 1 fires every 0.25 seconds; timer 2 every 0.5 seconds; etc</span>
<span class="k">for</span> <span class="n">i</span><span class="p">,</span> <span class="n">fd</span> <span class="ow">in</span> <span class="nb">enumerate</span><span class="p">(</span><span class="n">fds</span><span class="p">,</span> <span class="n">start</span><span class="o">=</span><span class="mi">1</span><span class="p">):</span>
<span class="n">one_sec_in_nsec</span> <span class="o">=</span> <span class="mi">10</span><span class="o">**</span><span class="mi">9</span>
<span class="n">i</span> <span class="o">=</span> <span class="n">i</span> <span class="o">*</span> <span class="n">one_sec_in_nsec</span>
<span class="n">os</span><span class="o">.</span><span class="n">timerfd_settime_ns</span><span class="p">(</span><span class="n">fd</span><span class="p">,</span> <span class="n">initial</span><span class="o">=</span><span class="n">i</span><span class="o">//</span><span class="mi">4</span><span class="p">,</span> <span class="n">interval</span><span class="o">=</span><span class="n">i</span><span class="o">//</span><span class="mi">4</span><span class="p">)</span>
<span class="n">timeout</span> <span class="o">=</span> <span class="mi">3</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">conn</span> <span class="o">=</span> <span class="kc">None</span>
<span class="n">is_active</span> <span class="o">=</span> <span class="kc">True</span>
<span class="k">while</span> <span class="n">is_active</span><span class="p">:</span>
<span class="c1"># Wait for the timer to expire for 3 seconds.</span>
<span class="c1"># epoll.poll() returns a list of (fd, event) pairs.</span>
<span class="c1"># fd is a file descriptor.</span>
<span class="c1"># sock and conn[=returned value of socket.accept()] are socket objects, not file descriptors.</span>
<span class="c1"># So use sock.fileno() and conn.fileno() to get the file descriptors.</span>
<span class="n">events</span> <span class="o">=</span> <span class="n">ep</span><span class="o">.</span><span class="n">poll</span><span class="p">(</span><span class="n">timeout</span><span class="p">)</span>
<span class="c1"># If more than one timer file descriptors are ready for reading at once,</span>
<span class="c1"># epoll.poll() returns a list of (fd, event) pairs.</span>
<span class="c1">#</span>
<span class="c1"># In this example settings,</span>
<span class="c1"># 1st timer fires every 0.25 seconds in 0.25 seconds. (0.25, 0.5, 0.75, 1.0, ...)</span>
<span class="c1"># 2nd timer every 0.5 seconds in 0.5 seconds. (0.5, 1.0, 1.5, 2.0, ...)</span>
<span class="c1"># 3rd timer every 0.75 seconds in 0.75 seconds. (0.75, 1.5, 2.25, 3.0, ...)</span>
<span class="c1">#</span>
<span class="c1"># In 0.25 seconds, only 1st timer fires.</span>
<span class="c1"># In 0.5 seconds, 1st timer and 2nd timer fires at once.</span>
<span class="c1"># In 0.75 seconds, 1st timer and 3rd timer fires at once.</span>
<span class="c1"># In 1.5 seconds, 1st timer, 2nd timer and 3rd timer fires at once.</span>
<span class="c1">#</span>
<span class="c1"># If a timer file descriptor is signaled more than once since</span>
<span class="c1"># the last os.read() call, os.read() returns the number of signaled</span>
<span class="c1"># as host order of class bytes.</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Signaled events=</span><span class="si">{</span><span class="n">events</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="k">for</span> <span class="n">fd</span><span class="p">,</span> <span class="n">event</span> <span class="ow">in</span> <span class="n">events</span><span class="p">:</span>
<span class="k">if</span> <span class="n">event</span> <span class="o">&</span> <span class="n">select</span><span class="o">.</span><span class="n">EPOLLIN</span><span class="p">:</span>
<span class="k">if</span> <span class="n">fd</span> <span class="o">==</span> <span class="n">sock</span><span class="o">.</span><span class="n">fileno</span><span class="p">():</span>
<span class="c1"># Check if there is a connection request.</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Accepting connection </span><span class="si">{</span><span class="n">fd</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="n">conn</span><span class="p">,</span> <span class="n">addr</span> <span class="o">=</span> <span class="n">sock</span><span class="o">.</span><span class="n">accept</span><span class="p">()</span>
<span class="n">conn</span><span class="o">.</span><span class="n">setblocking</span><span class="p">(</span><span class="kc">False</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Accepted connection </span><span class="si">{</span><span class="n">conn</span><span class="si">}</span><span class="s2"> from </span><span class="si">{</span><span class="n">addr</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="n">ep</span><span class="o">.</span><span class="n">register</span><span class="p">(</span><span class="n">conn</span><span class="p">,</span> <span class="n">select</span><span class="o">.</span><span class="n">EPOLLIN</span><span class="p">)</span>
<span class="k">elif</span> <span class="n">conn</span> <span class="ow">and</span> <span class="n">fd</span> <span class="o">==</span> <span class="n">conn</span><span class="o">.</span><span class="n">fileno</span><span class="p">():</span>
<span class="c1"># Check if there is data to read.</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Reading data </span><span class="si">{</span><span class="n">fd</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="n">data</span> <span class="o">=</span> <span class="n">conn</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">if</span> <span class="n">data</span><span class="p">:</span>
<span class="c1"># You should catch UnicodeDecodeError exception for safety.</span>
<span class="n">cmd</span> <span class="o">=</span> <span class="n">data</span><span class="o">.</span><span class="n">decode</span><span class="p">()</span>
<span class="k">if</span> <span class="n">cmd</span><span class="o">.</span><span class="n">startswith</span><span class="p">(</span><span class="s2">"stop"</span><span class="p">):</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Stopping server"</span><span class="p">)</span>
<span class="n">is_active</span> <span class="o">=</span> <span class="kc">False</span>
<span class="k">else</span><span class="p">:</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Unknown command: </span><span class="si">{</span><span class="n">cmd</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="c1"># No more data, close connection</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Closing connection </span><span class="si">{</span><span class="n">fd</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="n">ep</span><span class="o">.</span><span class="n">unregister</span><span class="p">(</span><span class="n">conn</span><span class="p">)</span>
<span class="n">conn</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="n">conn</span> <span class="o">=</span> <span class="kc">None</span>
<span class="k">elif</span> <span class="n">fd</span> <span class="ow">in</span> <span class="n">fds</span><span class="p">:</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Reading timer </span><span class="si">{</span><span class="n">fd</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="n">count</span> <span class="o">=</span> <span class="nb">int</span><span class="o">.</span><span class="n">from_bytes</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">read</span><span class="p">(</span><span class="n">fd</span><span class="p">,</span> <span class="mi">8</span><span class="p">),</span> <span class="n">byteorder</span><span class="o">=</span><span class="n">sys</span><span class="o">.</span><span class="n">byteorder</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Timer </span><span class="si">{</span><span class="n">fds</span><span class="o">.</span><span class="n">index</span><span class="p">(</span><span class="n">fd</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="si">}</span><span class="s2"> expired </span><span class="si">{</span><span class="n">count</span><span class="si">}</span><span class="s2"> times"</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Unknown file descriptor </span><span class="si">{</span><span class="n">fd</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="k">finally</span><span class="p">:</span>
<span class="k">for</span> <span class="n">fd</span> <span class="ow">in</span> <span class="n">fds</span><span class="p">:</span>
<span class="n">ep</span><span class="o">.</span><span class="n">unregister</span><span class="p">(</span><span class="n">fd</span><span class="p">)</span>
<span class="n">os</span><span class="o">.</span><span class="n">close</span><span class="p">(</span><span class="n">fd</span><span class="p">)</span>
<span class="n">ep</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</pre></div>
</div>
<p>This example shows how <a class="reference internal" href="../library/select.html#select.select" title="select.select"><code class="xref py py-func docutils literal notranslate"><span class="pre">select()</span></code></a> can be used with timer file
descriptors to wait until the file descriptor is ready for reading:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">os</span><span class="o">,</span><span class="w"> </span><span class="nn">time</span><span class="o">,</span><span class="w"> </span><span class="nn">select</span><span class="o">,</span><span class="w"> </span><span class="nn">socket</span><span class="o">,</span><span class="w"> </span><span class="nn">sys</span>
<span class="c1"># In this example, use loopback address to send "stop" command to the server.</span>
<span class="c1">#</span>
<span class="c1"># $ telnet 127.0.0.1 1234</span>
<span class="c1"># Trying 127.0.0.1...</span>
<span class="c1"># Connected to 127.0.0.1.</span>
<span class="c1"># Escape character is '^]'.</span>
<span class="c1"># stop</span>
<span class="c1"># Connection closed by foreign host.</span>
<span class="c1">#</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">bind</span><span class="p">((</span><span class="s2">"127.0.0.1"</span><span class="p">,</span> <span class="mi">1234</span><span class="p">))</span>
<span class="n">sock</span><span class="o">.</span><span class="n">setblocking</span><span class="p">(</span><span class="kc">False</span><span class="p">)</span>
<span class="n">sock</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="c1"># Create timer file descriptors in non-blocking mode.</span>
<span class="n">num</span> <span class="o">=</span> <span class="mi">3</span>
<span class="n">fds</span> <span class="o">=</span> <span class="p">[</span><span class="n">os</span><span class="o">.</span><span class="n">timerfd_create</span><span class="p">(</span><span class="n">time</span><span class="o">.</span><span class="n">CLOCK_REALTIME</span><span class="p">,</span> <span class="n">flags</span><span class="o">=</span><span class="n">os</span><span class="o">.</span><span class="n">TFD_NONBLOCK</span><span class="p">)</span>
<span class="k">for</span> <span class="n">_</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">num</span><span class="p">)]</span>
<span class="n">select_fds</span> <span class="o">=</span> <span class="n">fds</span> <span class="o">+</span> <span class="p">[</span><span class="n">sock</span><span class="p">]</span>
<span class="c1"># Start the timers with os.timerfd_settime() in seconds.</span>
<span class="c1"># Timer 1 fires every 0.25 seconds; timer 2 every 0.5 seconds; etc</span>
<span class="k">for</span> <span class="n">i</span><span class="p">,</span> <span class="n">fd</span> <span class="ow">in</span> <span class="nb">enumerate</span><span class="p">(</span><span class="n">fds</span><span class="p">,</span> <span class="n">start</span><span class="o">=</span><span class="mi">1</span><span class="p">):</span>
<span class="n">os</span><span class="o">.</span><span class="n">timerfd_settime</span><span class="p">(</span><span class="n">fd</span><span class="p">,</span> <span class="n">initial</span><span class="o">=</span><span class="n">i</span><span class="o">/</span><span class="mi">4</span><span class="p">,</span> <span class="n">interval</span><span class="o">=</span><span class="n">i</span><span class="o">/</span><span class="mi">4</span><span class="p">)</span>
<span class="n">timeout</span> <span class="o">=</span> <span class="mi">3</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">conn</span> <span class="o">=</span> <span class="kc">None</span>
<span class="n">is_active</span> <span class="o">=</span> <span class="kc">True</span>
<span class="k">while</span> <span class="n">is_active</span><span class="p">:</span>
<span class="c1"># Wait for the timer to expire for 3 seconds.</span>
<span class="c1"># select.select() returns a list of file descriptors or objects.</span>
<span class="n">rfd</span><span class="p">,</span> <span class="n">wfd</span><span class="p">,</span> <span class="n">xfd</span> <span class="o">=</span> <span class="n">select</span><span class="o">.</span><span class="n">select</span><span class="p">(</span><span class="n">select_fds</span><span class="p">,</span> <span class="n">select_fds</span><span class="p">,</span> <span class="n">select_fds</span><span class="p">,</span> <span class="n">timeout</span><span class="p">)</span>
<span class="k">for</span> <span class="n">fd</span> <span class="ow">in</span> <span class="n">rfd</span><span class="p">:</span>
<span class="k">if</span> <span class="n">fd</span> <span class="o">==</span> <span class="n">sock</span><span class="p">:</span>
<span class="c1"># Check if there is a connection request.</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Accepting connection </span><span class="si">{</span><span class="n">fd</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="n">conn</span><span class="p">,</span> <span class="n">addr</span> <span class="o">=</span> <span class="n">sock</span><span class="o">.</span><span class="n">accept</span><span class="p">()</span>
<span class="n">conn</span><span class="o">.</span><span class="n">setblocking</span><span class="p">(</span><span class="kc">False</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Accepted connection </span><span class="si">{</span><span class="n">conn</span><span class="si">}</span><span class="s2"> from </span><span class="si">{</span><span class="n">addr</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="n">select_fds</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">conn</span><span class="p">)</span>
<span class="k">elif</span> <span class="n">conn</span> <span class="ow">and</span> <span class="n">fd</span> <span class="o">==</span> <span class="n">conn</span><span class="p">:</span>
<span class="c1"># Check if there is data to read.</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Reading data </span><span class="si">{</span><span class="n">fd</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="n">data</span> <span class="o">=</span> <span class="n">conn</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">if</span> <span class="n">data</span><span class="p">:</span>
<span class="c1"># You should catch UnicodeDecodeError exception for safety.</span>
<span class="n">cmd</span> <span class="o">=</span> <span class="n">data</span><span class="o">.</span><span class="n">decode</span><span class="p">()</span>
<span class="k">if</span> <span class="n">cmd</span><span class="o">.</span><span class="n">startswith</span><span class="p">(</span><span class="s2">"stop"</span><span class="p">):</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Stopping server"</span><span class="p">)</span>
<span class="n">is_active</span> <span class="o">=</span> <span class="kc">False</span>
<span class="k">else</span><span class="p">:</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Unknown command: </span><span class="si">{</span><span class="n">cmd</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="c1"># No more data, close connection</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Closing connection </span><span class="si">{</span><span class="n">fd</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="n">select_fds</span><span class="o">.</span><span class="n">remove</span><span class="p">(</span><span class="n">conn</span><span class="p">)</span>
<span class="n">conn</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="n">conn</span> <span class="o">=</span> <span class="kc">None</span>
<span class="k">elif</span> <span class="n">fd</span> <span class="ow">in</span> <span class="n">fds</span><span class="p">:</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Reading timer </span><span class="si">{</span><span class="n">fd</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="n">count</span> <span class="o">=</span> <span class="nb">int</span><span class="o">.</span><span class="n">from_bytes</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">read</span><span class="p">(</span><span class="n">fd</span><span class="p">,</span> <span class="mi">8</span><span class="p">),</span> <span class="n">byteorder</span><span class="o">=</span><span class="n">sys</span><span class="o">.</span><span class="n">byteorder</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Timer </span><span class="si">{</span><span class="n">fds</span><span class="o">.</span><span class="n">index</span><span class="p">(</span><span class="n">fd</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="si">}</span><span class="s2"> expired </span><span class="si">{</span><span class="n">count</span><span class="si">}</span><span class="s2"> times"</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Unknown file descriptor </span><span class="si">{</span><span class="n">fd</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="k">finally</span><span class="p">:</span>
<span class="k">for</span> <span class="n">fd</span> <span class="ow">in</span> <span class="n">fds</span><span class="p">:</span>
<span class="n">os</span><span class="o">.</span><span class="n">close</span><span class="p">(</span><span class="n">fd</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="n">sock</span> <span class="o">=</span> <span class="kc">None</span>
</pre></div>
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