SIPSorcery: Problem with RTP packet receiving

Question

I have a .Net Core application that is the back-end of my application. In it, I am using the SIPSorcery library as a bridge between a SIP Server and my front-end application.

Basically, I forward every RTP packet received via RTPSession to an RTCPeerConnection and vice versa, according to the example in the library.

This works very well when I run my application on localhost (I only had a small problem with the Firewall that I resolved without difficulty), but when I deploy the same application on a Windows Server the RTP packets never arrive, even with all the ports released by the firewall .

I started to suspect some problem related to the Codec. Do I need to have something previously installed on the virtual machine for this to work well?

A sample code for creating RTP Session in my application:

RTPSession session = new(false, false, false, portRange: new(51200, 52399))
{
    AcceptRtpFromAny = true
};
session.OnStarted += () => SendMessage("RTPSession Started", null);
session.OnClosed += () => SendMessage("RTPSession Closed", null);

session.OnRtpPacketReceived += (_, mediaType, rtpPacket) =>
{
    if (!_peerConnections.Any() || mediaType != SDPMediaTypesEnum.audio) return;
    _peerConnections.ForEach(peer =>
    {
        try
        {
            peer.PeerConnection.SendAudio((uint)rtpPacket.Payload.Length, rtpPacket.Payload);
        }
        catch
        {
            DisconnectPeerConnection(peer, "Erro na transmissão do pacote de áudio.");
        }
    });
};
MediaStreamTrack audioTrack = new(SDPMediaTypesEnum.audio, false, new List<SDPAudioVideoMediaFormat> { new SDPAudioVideoMediaFormat(SDPWellKnownMediaFormatsEnum.PCMU) });

session.addTrack(audioTrack);

Then, I answer the call (already accepted previously) with the created session:

await _sipUserAgent.Answer(sipIncomingCall, session);

Important information is that the SIP server is correctly configured to accept my connection, the problem is not on that side.

After deploying to IIS on Windows Server 2022, I ran the same tests I had done on localhost. Everything worked fine, until I tried to answer a call, in which no RTP packet was received, even though the UDP connection was opened.