Thanks Daniel. I got it basically working with the following config. But there is one last bug. If client B connected and registered, then disconnected without proper unregister, it seems the location table didn't get prompt update. If client A sends Invite right after that, the sip server will try to connect to B(which will surely fail since B is behind the firewall), instead of sending 480 to A right away. Is there a way to fix this? Thanks. JJ if (is_method("REGISTER")) { # authenticate the REGISTER requests (uncomment to enable auth) if (!www_authorize("", "subscriber")) { www_challenge("", "0"); exit; } if (!db_check_to()) { sl_send_reply("403","Forbidden auth ID"); exit; } if (!save("location", "m")) sl_reply_error(); exit; } if (!lookup("location")) { #if (!registered("location")) { sl_send_reply("480","Not Found"); exit; } if (!registered("location")) { sl_send_reply("480","Not Found"); exit; } if(!t_relay()) { sl_send_reply("500", "relaying failed"); } exit; *From:*Daniel-Constantin Mierla [mailto:miconda@gmail.com] *Sent:* Wednesday, September 28, 2011 2:49 AM *To:* SIP Router - Kamailio (OpenSER) and SIP Express Router (SER) - Users Mailing List *Cc:* JJ Zeng *Subject:* Re: [SR-Users] simple question but can't find the answer Hello, On 9/28/11 2:43 AM, JJ Zeng wrote: Hi, I am really new to ser(just installed it today). My situation is here: Both A and B make tcp connection to ser proxy server. If A sends "Invite" to B, ser would look up the tcp connection of B, and relay the sip request. If B is not connected, then 480 is returned to A. When B sends back the response, ser would relay it to A. It looks really simple, but I just can't figure out how to do it. what default config file you started with? Apart of that when the user is not online, the default config replies with 404 Not Found, the relaying between phones when they are online is done there, being a combination of calling function from registrar and tm modules. So, if you start with the default config, no matter is Kamailio or SER flavour, routing of the calls between online users is provided there, just go through it in order to understand better. Cheers, Daniel -- Daniel-Constantin Mierla --http://www.asipto.com Kamailio Advanced Training, Oct 10-13, Berlin:http://asipto.com/u/kat http://linkedin.com/in/miconda -- http://twitter.com/miconda _______________________________________________ SIP Express Router (SER) and Kamailio (OpenSER) - sr-users mailing list sr-users(a)lists.sip-router.org http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users