title: How do I choose a multicast address for my application's use?
body: <p>How should I choose an IPv4 multicast address for my application's use? I may need more than one (a whole range perhaps ultimately) but just want to avoid conflicts with other applications.</p>
  
  <ul>
  <li>Packets will be entirely contained within an administrative domain, probably a LAN</li>
  <li>If several independent instances of my application are in use on the same network, they could each use their own multicast address - but if they don't, they will be able to coexist anyway, they'll just have a small amount of overhead ignoring each others' packets.</li>
  <li>My packets already contain a "magic number" to avoid problems</li>
  <li>I will be checking the originator address (which I know can be spoofed of course), TTL and other things to try to prevent unexpected packets mucking things up.</li>
  </ul>
  
  <p>Ideas please :)</p>
  
  <p>Currently I've just allocated an arbitrary one from the "local use" space, 239.255.42.99</p>