send ACK request failed: transport.UnsupportedProtocolError: protocol TLS is not supported

[mostafafarzaneh]

Hey there,

I am trying to connect to my Webex meeting using the client example.
The library sends an "INVITE" request to the server. The server responses with "Trying", "Ringing", and finally "OK". Here is the "OK" response:

Via: SIP/2.0/TCP 192.168.0.115:5080;branch=z9hG4bK.vWHLeFU2E7W76whrkBCh9Q5MiyNfRd5F
Record-Route: <sip:l2sip-aore-01.wbx2.com:5062;transport=tls;lr>
Record-Route: <sip:rr$n=net_me_tls_l2sip@209.197.207.55:5060;transport=tcp;lr;bypassvcs=true>
To: <sip:XXXXXXXX@meet93.webex.com>;tag=77899554
From: "goSIP/example-client" <sip:6666@192.168.0.115;transport=tcp>;tag=FWwqwkFA
Contact: <sip:l2sip-UA@l2sip-aore-01.wbx2.com:5062;transport=tls>;isfocus
Call-ID: 5IyihuOqPiUgXGHx9452tJ3HN5qBqV3u
CSeq: 1 INVITE
Content-Length: 287
Session-ID: 340af0dbc2569b63b00c4706ce7a35d0;remote=ef15ce9d3dca30c6ae3aefd3e42d66de
Locus: 184d96d5-757a-3279-b289-16d139e9e35c
Locus-SessionId: 340af0db-c256-9b63-b00c-4706ce7a35d0
Locus-Type: MEETING
WebexMeetingNumber: XXXXXXXX
User-Agent: Cisco-L2SIP
Accept: application/sdp
Allow: INVITE, ACK, CANCEL, BYE, REFER, INFO, OPTIONS, NOTIFY, SUBSCRIBE
Allow-Events: kpml
Supported: replaces
Content-Type: application/sdp

Which contains Record-Route header field. After receiving this message, the library wants to respond with an "ACK" message. Here is the error:

[2021-06-08 12:02:01.568] ERROR SipStack: send ACK request failed: transport.UnsupportedProtocolError: protocol TLS is not supported ack_request=sip.Request<recipient=sip:l2sip-UA@l2sip-aore-01.wbx2.com:5062;transport=tls transaction_key=z9hG4bK.vWHLeFU2E7W76whrkBCh9Q5MiyNfRd5F__INVITE sent_at=2021-06-08 12:02:01.568402932 +0430 +0430 m=+3.146215901 request_id=2121ffc5-c694-48e2-8880-783458cae0c9 transaction_ptr=0xc000179d40 method=ACK invite_request_id=d2f5a7c3-2871-48a2-b1f9-c658d05d7e07 invite_response_id=255ef8b0-d4ab-413d-9b42-c05a4ee863bf sequence=1> invite_request=sip.Request<method=INVITE recipient=sip:XXXXXXXX@meet93.webex.com;transport=tcp sequence=1 request_id=d2f5a7c3-2871-48a2-b1f9-c658d05d7e07 transaction_ptr=0xc000179d40 transaction_key=z9hG4bK.vWHLeFU2E7W76whrkBCh9Q5MiyNfRd5F__INVITE> invite_response=sip.Response<reason=OK method=INVITE sequence=1 response_id=255ef8b0-d4ab-413d-9b42-c05a4ee863bf connection_key=tcp:209.197.207.55:5060 received_at=2021-06-08 12:02:01.567166135 +0430 +0430 m=+3.144979233 request_id=d2f5a7c3-2871-48a2-b1f9-c658d05d7e07 status=200>

[cloudwebrtc]

It seems that the ACK did not pass through the Record-Route return path correctly.
I guess the final ACK is sent using the address in
Contact: <sip:l2sip-UA@l2sip-aore-01.wbx2.com:5062;transport=tls>;isfocus.

You can try to trace the code, if so, I think it should be a bug.