A couple of weeks ago, Thiago helped me out understand the basics of JIngle Relay Nodes. He explained that, the server needs to open 4 ports and transfer data coming into them with each one of the other. His exact email

In fact your server will have to open 4 ports in total, 1rtp+ 1rtcp
for each end point.
Lets call them A, A', B, B' respectively.

Every packet that arrives at A needs to be sent through B to whichever
address(IP:Port) is sending to B.
Every packet that arrives at A' needs to be sent through B' to
whichever address(IP:Port) is sending to B'.
Every packet that arrives at B needs to be sent through A to whichever
address(IP:Port) is sending to A.
Every packet that arrives at B' needs to be sent through A' to
whichever address(IP:Port) is sending to A'.

Exception:
* If no packet was received in a given port, packets to be sent
through that port should be discarded.

Remarks:
* There is no process to verify that a sender to a given port is the
real sender of the stream. The recommended mitigation is to create a
race of packets, for the latest 10 received packets in a given port,
only relay and update Address to the one sender holding the majority
of the packets.

I ended up implementing the same in TCP. mod_jinglerelaynodes.lua and mod_jinglechannel.lua