VoIP using PjSIP : pjsua_acc.c SIP registration failed, status=408 (Request Timeout)

I am trying to run test VoIP program as given in http://www.pjsip.org/pjsip/docs/html/page_pjsi开发者_Go百科p_sample_simple_pjsuaua_c.htm

I am trying public SIP servers present at http://www1.cs.columbia.edu/sip/servers.html

But I always get error message as

14:33:25.515 pjsua_acc.c SIP registration failed, status=408 (Request Timeout)

I never used SIP before, I am not able to guess where the problem is. Is there any simple way to test SIP servers? Does anybody know public free SIP server that works?

Thanks

The 408 timeout message typically means that the user agent, in this case your pjsip application, sent it's request but did not get a response.

I'm involved in a free SIP service called sipsorcery that you can test your software with. It lets you view a full trace of your SIP messages with either a Silverlight browser application or telnet console which is extremely handy when trying to troubleshoot.

You can test your SIP client locally with SIPP. It can process REGISTER requests as well as all other SIP messages. In addition you can write xml scripts for SIPP for other complex scenarios.