pan class="keyword">void</span> <span class="identifier">handler</span><span class="special">(</span>
  <span class="comment">// Result of operation. if the sequence is empty, set to</span>
  <span class="comment">// boost::asio::error::not_found. Otherwise, contains the</span>
  <span class="comment">// error from the last connection attempt.</span>
  <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="spe