BlackBerry SIP communication

I am trying to enable the SIP communication in BlackBerry. I am developing an application to call from BlackBerry simulators. I came across the MJSIP api, which is used for the SIP communication.

But still I am not clear about the basic req开发者_开发百科uirements for my application, like if any server is needed?

If a server is needed then which server should I use? and how do I configure my simulators with that server?

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I'm not sure exactly what you are asking, but here is some information that might help.

In principle SIP clients can connect directly to each other without a server in between. However, direct SIP connections do not work very well if either client is behind a firewall which does NAT (e.g. you might not be able to initiate a call with them, or if you do then you might get one-way audio). This problem is often solved by having all clients register with a SIP proxy, who can keep a communications channel alive to the client through a firewall by sending SIP REGISTER messages. So most commercial solutions will require a SIP proxy for all clients to register with.

Another Stackoverflow question links to a incomplete tutorial on MJSIP:
how to use mjsip with j2me

It seems that MJSIP is released under a GNU GPL license, which means if you use it then you'll need to release your source code under GPL too, which is probably not going to fly if you are writing a commercial application.
http://supportforums.blackberry.com/t5/Java-Development/mjsip-GNU-GPL-license/m-p/283607

FYI, when testing, you usually need to start the MDS simulator in order for the BlackBerry simulator to be able to connect to the internet.
Display simple HTML in a native BlackBerry application