RTP Stream plays on WiFi but 3G netowrk - PLEASE,PLEASE,PLEASE HELP :(

[Guest asadi.alireza]

hi there,

I have developed a SIP based voip application, I have a Server(Written in c# and two android client application(which is written based on the Native Sip Stack of Android 2.3).

The SIP registration works perfect and beside that streaming and playing of my voice also works perfect over WiFi network but when i switch my network to 3G I cannot hear the voice(the SIP registration works without any problem).

I trace the network, and I found out that stream passes my 3G network, but the android clients cannot play it, and one more thing that I tested was that If I change one of my client from android to a simple c# desktop application, even in 3G network everything works fine(it shows that my 3g network does not have any problem) and streaming and playing the voice works without any problem.

please someone help me how can i hear this stream which is created by Native SIP Stack in a 3G network?

PLEASE PLEASE PLEASE HELP ME, I GOOGLED, TESTED EVERY THING in the past 3 weeks but could not find any solution