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Full Discussion: TCP connection check
Top Forums Programming TCP connection check Post 302531865 by Loic Domaigne on Saturday 18th of June 2011 09:17:39 AM
Old 06-18-2011
Quote:
Originally Posted by Shang
Hi.
I am writing client - server application using TCP sockets.
I need some very basic functionality, namely: how to check if another "participant" of the connection is still present?
I want to handle situations, when client is gone, or server breaks down, etc.
You must first be prepared that the server close unexpectedly the connection (e.g. due to a crash), that is:
  • read returns -1 and errno is set (e.g. ECONNRESET).
  • write cause SIGPIPE to be sent to your process. The classical way to handle this is to ignore SIGPIPE, in which case write() shall fail and set errno to EPIPE.
This is however usually not enough to cover all scenarios (e.g. when the connection get physically broken, well simulated by plugging the "internet cable" out). Depending on our context, you may need to have a heartbeat mechanism, that is a way to exchange message between client and server to verify the aliveness of the connection.

If applicable, you may want to check the keep alive feature offered by TCP (there are however some pitfalls), our roll your own heartbeat mechanism in the protocol.

HTH, Loïc
 

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LEARN ABOUT REDHAT

tcp-env

tcp-env(1)                                                    General Commands Manual                                                   tcp-env(1)

NAME

       tcp-env - set up TCP-related environment variables

SYNOPSIS

       tcp-env [ -rR ] [ -ttimeout ] program [ arg ...  ]

DESCRIPTION

       The  input  for  tcp-env  must be a TCP connection.  tcp-env finds out information about that connection, puts the information into several
       environment variables as described in tcp-environ(5), and runs program with the given arguments.

       Usually tcp-env is run from inetd.  It might instead be run from another server that already sets up the right  environment  variables;  if
       PROTO  is  set  to  TCP  when  tcp-env  is invoked, tcp-env assumes that all the other variables are set up properly, and it does not check
       whether the input is a TCP connection.

OPTIONS

       -r     (Default.)  Attempt to obtain TCPREMOTEINFO from the remote host.

       -R     Do not attempt to obtain TCPREMOTEINFO from the remote host.

       -ttimeout
              Give up on the TCPREMOTEINFO connection attempt after timeout seconds.  Default: 30.

SEE ALSO

       tcp-environ(5), inetd(8)

                                                                                                                                        tcp-env(1)
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