LISTEN/NOTIFY problem

Hi everybody,
I've got a weird problem with LISTEN/NOTIFY.

My C++ app subscribes for the notifications, just like in libpq examples:
http://www.postgresql.org/docs/8.3/static/libpq-example.html

The only difference, that I am setting the timeout on select just to check
if application wants to exit.

//open session

//subscribe

while(!exit)
{
sock = PGsocket(conn)

res = select(sock);

if (res)

//check if it timeout
//or if there was a notification

}

The problem that I am facing is that after some time notifications stop
coming.
select() returns on timeout and nothing else.

Just as a test a included UNLISTEN/LISTEN sequence into the loop, so after
timeout or event application re-subscribes. And this helps.

The question is, what I am doing wrong with the code in the first place?

Any help is appreciated.

Cheers,
Dmitri.

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