[Kamailio-Users] no free tcp receiver

Klaus Darilion klaus.mailinglists at pernau.at
Tue Dec 2 20:57:30 CET 2008

Gawith wrote:
> Klaus Darilion schrieb:
>> How many TCP worker processes do you have (tcp_children)?
>> How busy is the server? requests/transactions per second
> That's the point. The server does nearly nothing:
> I have 10 TCP childs and only about 2 INVITEs/sec.

Then there is probably something going wrong.

I would:
- stop the proxy and all clients
- start tcpdump or wireshark (without capture filter)
- start the clients (if you have clients)
- make a single call, hang up
- repeat the single call, hang up.

Then analyze the capture file: Are there "strange" SYN packets trying to 
establish a connection which does not work? Are there other TCP errors 
(RST, FIN ...)

I suspect that workers are trying to establish new tcp connection which 
do trigger a timeout - and as TCP handling in Kamailio is blocking the 
TCP workers are busy when new requests are received.

Note: With "TCP receiver" I mean the single process which handles 
incoming TCP SIP messages and forwards the messages to the TCP worker 
processes (the number of TCP workers are configured with tcp_children).
Thus, IMO the warning message in the log file is wrong because it is 
talking about TCP receivers although the TCP workers are meant.

You could also adjust the various TCP timeout settings to shorter value 
- but I recommend to use default value (large timeouts) as this will 
help you to identify the problem.


> Regards
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