title: How to monitor page for changes without polling?
body: <p>I currently have an IRC bot written in C++ which monitors a page written in php for changes and then outputs these changes to the IRC channel.
  However the current method is rather in-effective as it just constantly polls the page once every 10 seconds and compares it to the last seen version to check if anything has changed.
  I can decrease the page check interval to about 2-3 seconds before the IRC bot starts to take a performance hit, however this isn't ideal. 
  Often the page I am monitoring can change multiple times within the 10 second period, so a change could be missed, what would be a better method to get the data from the page? considering I control both the page written in PHP, and the IRC bot, but they are on different servers. </p>
  
  <p>The sole purpose of this page is to pass data to the IRC bot, so it could be completely re-implemented as something else if that would be a better solution; the IRC bot also monitors multiple versions of this page to check for different things.</p>