TCP Call Fails with SIP 503 Error (Service Unavailable), Despite Working in Linphone App

[savan15]

Describe the bug
I'm encountering an issue with placing SIP calls over TCP using the library. The SIP extension registers successfully, but when I try to place a call, it fails with the following error:

Call failed with cause: Code: [503], Cause: SIP Failure Code, Reason: Service Unavailable
[2025-05-05 17:30:24.897] Level.debug invite_client.dart:90 ::: Timer D expired for transaction z9hG4bK8376025900000000
D/FlutterWebRTCPlugin(11825): onConnectionChangeCLOSED

Additional Info
I have tested the same SIP extension with TCP on the same device using the Linphone Android application, and it works fine there.

Please let me know if any further logs or details are needed.

[savan15]

@mikaelwills
?

[mikaelwills]

Yea this looks like one of the points in the FAQ section of this repo, similar to the usual codecs mismatch issue maybe

[savan15]

Thank you for the guidance! I was able to resolve the previous error (503 Service Unavailable) by explicitly setting the contact URI in the settings as follows:

settings.contact_uri =
    'sip:${_authorizationUserController.text}@${await IpAddress().getIp()};transport=tcp';

After making this change, the 503 error is no longer occurring. However, I'm now encountering a new issue:

Call failed with cause: Code: [603], Cause: Rejected, Reason: Decline

The SIP extension registers successfully, and I’ve verified that the same extension works over TCP on the same device using the Linphone Android application.

Please let me know if you need additional logs or details to help diagnose this new error.

Thanks again for your support!

[savan15]

Could you please assist me in resolving this issue?
Your guidance would be greatly appreciated. Thank you!