[JDEV] Heartbeat patch for dialup and laptop users and faulty presence info

[Mark Harrison]

Would it be possible somehow to combine the ping-only with a ping-pong 
system in some way? As I understand it, the current ping only system uses 
whitespace and relies on tcp to detect connection losses (correct me if 
I'm wrong).

If a client connects that supports replying to the ping, then it could 
reply in the same way (whitespace), if not, then obviously no reply would 
be sent and the tcp method would (more slowly) detect the disconnect.

The server would have to decide if the client supports the ping-pong 
method, perhaps by assuming it doesn't until a reply is sent, 
signifying that the client does in fact support this mechanism, and 
disconnecting the client if it fails to reply to further probes.

Of course, there is still bandwidth to worry about, but this could allow 
compatibility with clients that do not support (or want to support) 
replying to the heartbeat, while allowing better notification of 
disconnects for those that do.

--
Mark Harrison <harrism1 at cs.man.ac.uk>