Hi All, I have set up Kamailio 3.3 on Ubuntu machine.I created two user test 1 and test 2. I could use Presence and also i was able to register to Kamailio server and exchange presence status with each other. Details- I used TCP protocol . testing methods - Linphone, a sample application. I am able to register succesfully with (TCP) on to kamailio server using Lin phone and sample application. I am able to update presence status of the users. Issue : When i try to send messages between two users ( using TCP ) 1. from Sample application, when i try to send message, i get 420 temporarily Unavailable error from server. 2. from Lin phone 3.5.2, i was able to send messages ( sue TCP) but when the other user try to reply back , i get same error 480 Temporarily Unavailable. error from server. I want a support to understand why i get error while sending messages with TCP via Kamailio server. I am able to succeesfully send and receive messages when i use UDP from my sample application and Lin phone. regards Sunil C