SIP server programming

I'm new to SIP/VoIP programming. I want to implement a SIP server mainly for registering and proxing. I know to start from scratch is foolishness, but then what options do I hav开发者_如何学运维e? I have been doing google-ing for a couple of days, and I got some few options to work with-

1. SIP JAIN
2. SIPServlet

Please comment on these items and some related materials. It would be helpful if someone can comment on the programming languages that suits SIP best, for all I'm more inclined towards Java.

Regards,

There are already some Open Source SIP proxy / registrars available: OpenSIPS and Kamailio. Both are written in C.

Do you have any specific need for writing a SIP proxy from scratch? Maybe you could extend one of the available ones to suit your needs?