I am having an issue when enabling Real-Time Text between two phones. These phones are custom phones that have the protocol T140 enabled. I have enabled T140 in the sip.conf file as well as the textsupport flag. When creating a call between the two phones, I can see the m values in a packet capture that shows all of the proper ports for audio and text and that the text protocol being used is T140. Once the call is placed, text starts flowing on both phones with repeated RTP (ex. RTPRTPRTPRTPRTPRTPRTP). This goes for the whole call.
I have noticed that if I try sending text, it will go through to the other phone and vice-versa. There is just a lot of gibberish with the RTP to really see it on the device. Looking at a packet capture, I can see the RTP text and my text going through. The RTP text looks like it only originates from the freepbx server whereas the text I send originates from the phone, like I’d expect.
Is the RTP message from freepbx some type of keep-alive that the phones are supposed to filter or am I missing something in my settings?