Max Conncection limit?

We start a server and initiate 30 connections(with the libpq C interface)
which are stored in a stack to use and and to be reused.

After awhile I try to start another server that will also try to initiate 30
connections, for each connection I then get a PQErrorMessage like that :
"Sorry, too many connections"

if I do a ps -ax at that time I get a lot of /usr/bin/postgres 192.168.0.1
user name passwd idle

what I usually do is restart postgres but I wish I didnt have to do that...
That is not an elegant solutuion any ways.
What can I do? Thanks in advance. Regards