Iñaki,
Thank you for your response.
You could be behind a fu***** SIP-ALG enabled router rewritting SIP requests "to fix the NAT". To detect if you router has SIP-ALG enabled you can try various options:
- Ensure you are not using STUN in your client so the request arriving to the
proxy should contain client private address in Via and Contact header.
I have checked the Via and Contact headers and they do contain the client private address. I am using an SMC7004VWBR wireless router thats about 8 years old. I have checked all the router settings and do not see any option to enable/disable SIP ALG, so i presume the router is not capable of rewriting SIP headers.
I will try your program out as another method of confirmation of the router's SIP ALG capability.
I have found that this anomaly (extra byte in Contact-Length header)occurs only while sending to the proxy on a specific port(5060). By changing the port on which the proxy listens(7160), the Contact-length header field is ok.
Is there a list of routers out there that we know for sure that are not SIP ALG capable ?
Once again, thanks for you suggestions. Regards, Vikram.