Reducing the timeout on a TCP connection

Dan Nelson dnelson at
Tue Aug 1 21:21:49 UTC 2006

In the last episode (Aug 01), Bill Moran said:
> In response to "Ted Mittelstaedt" <tedm at>:
> > This is why the snmp protocol uses UDP, Bill.
> > 
> > You need to use something other than TCP for
> > monitoring.
> Well ... if I'm monitoring a server that uses TCP (PostgreSQL) I
> can't rightly establish whether or not it's successfully accepting
> connections unless I used TCP as well.

What I do is ping the target server first, with a small (1s) timeout.
If the ping fails, I don't try the TCP socket.  If the ping succeeds, I
know the TCP connection will either complete or fail immediately.

Another option is to do non-blocking connects to as many servers as you
have fds available, and select()/poll()/kqueue() for the results.  that
way at least you're checking other machines while waiting for the few
dead ones.

	Dan Nelson
	dnelson at

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