Hi Charles, 

I don't think your issue is rport, make sure you are setting the Contact header correctly.

Have you checked this blog post: https://skalatan.de/en/blog/kamailio-sbc-teams ?

There is a specific section that talks about how to tell Kamailio to send the OPTIONS like MS Teams wants them. 

Good luck, 
Joel.

On Thu, Jan 7, 2021 at 4:32 PM Charles Phillips <charles@rustybike.com> wrote:
Hello all.  As they say in radio, “long time listener, first time caller”

Anyway, I am having trouble getting past the following road block and any help would be greatly appreciated.

Kamailio version is 5.4.3 

When attempting to use dispatcher to send OPTIONS packets to several TLS destinations, the packets are leaving the Kamailio server on random ports.  This is a problem because the servers I am sending the OPTIONS to (MS Teams) are enforcing rport so the responses are returned to a port that Kamailio is not listening on.  I have tried to force the socket in the event route (relevant parts of snippet below) but it does not appear to help.  I should also mention that I am not behind NAT and the TLS socket is specified in the dispatcher attrs. 

event_route[tm:local-request] {
    sip_trace();


    $fs = “tls:**ip-address**:5061”;


}

I have used Kamailio as a TLS server for many projects, but this is my first time as a client.  I am sure I am missing something.

- Charles




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