Hello,
Alex, Klaus thank you for your replies.
Usually the softphones register to the proxy or SIP server. Thus, the proxy or SIP server knows under which IP:port (The IP:port from which the REGISTER was received) it can contact the sofpthone.
Yes, the softphones are registered to the SIP server, and hence the SIP server has the IP:port information required to contact the softphone. However, the SIP server does not include the port number in the R-URI of the INVITE that it generates.
This port number is dynamically assigned by the firewall and is not fixed, so manipulating the pseudo variable $rp by assigning it a fixed number will not work.
If it is not mandatory to include the port number in the R-URI, how does the proxy determine the port to which the SIP message must be forwarded ?
Thanks and Regards, Vikram.