Auto disconnect when idle? Flood?

It's normally a problem caused by routers which assume that, when there's no traffic for a certain period of time, the connection is no longer in use and just hasn't been closed correctly, so they kill it. The client only tends to notice this when it actually attempts to send something. If it's happening to only a few of your players, it's likely their routers/connections, but if it's happening to all then it's probably on the server's end. Aside from checking your router settings to extend the time period/turn this off, there are a couple of things you can do. They basically all send something to/from the server at regular intervals which is ignored, so the router sees that the connection is still in use and doesn't close it:

1) Change the keepalive_timeout setting in mush.cnf to something sufficiently small. Whether or not this works is dependant on the OS of the server, I believe, but doesn't require any kind of support from the players.

2) Set the KEEPALIVE flag on your players. This sends a Telnet code to the client which is ignored, but the act of sending it keeps the connection alive. Only works for players whose clients support Telnet negotiation, though.

3) Get your players to set up timers in their clients to send the IDLE command to the MUSH at regular intervals. This one should always work, but requires all of your players to actually set it up (and to have clients that support doing it), so is potentially the most problematic.

There might be other/better ways, but those are the ones I'm aware of. Hope that helps :)