Path: utzoo!mnetor!uunet!husc6!bbn!fkittred
From: fkittred@bbn.COM (Fletcher Kittredge)
Newsgroups: comp.unix.wizards
Subject: Re: AF_INET Stream Sockets & Server/Client Models
Message-ID: <744@cc6.bbn.COM>
Date: 12 Jan 88 13:20:06 GMT
References: <573@usl-pc.UUCP>
Reply-To: fkittred@cc6.bbn.com.BBN.COM (Fletcher Kittredge)
Followup-To: fkittred@cc6.bbn.com
Organization: Bolt Beranek and Newman Inc., Cambdridge MA
Lines: 15
Keywords: socket, pipe, signal
Summary: signal generated by broken socket connection

[ how can you tell if one end of a socket connection has abnormally
  terminated?]

    On Ultrix (BSD 4.[23] type) systems, if a process which has an
UNIX domain socket open dies (your client), the process on the other
end of the socket (your server) will receive the signal EPIPE when the
server attempts to write to the socket.

    Using the SO_KEEPALIVE socket option causes messages to be
periodically transmitted on a socket to test the state of the socket.
If you set your socket options correctly, when client doesn't respond
to the keepalive messages, then the EPIPE signal should be generated
for the server.  You can catch this signal and do whatever.

fletcher