They come back to the sending IP:port combination.
Think of the connections as a virtual circuit, linking a unique sending IP:port to a unique receiving IP:port.
The outbound to Fred will be:
From QDXIP:ephemeralPort1 to FredIP:12345
The outbound to George will be:
From QDXIP:ephemeralPort2 to GeorgeIP:12345
So messages sent to Fred will leave from QDXIP:ephemeralPort1 and go to FredIP:12345. When Fred sends an ack it will go back the way it came and be received by the “outbound to Fred” thread on QDXIP:ephemeralPort1.
Same with messages sent to George – they will leave from QDXIP:ephemeralPort2 and go to GeorgeIP:12345. When George sends an ack it will go back the way it came and be received by the “outbound to George” thread on QDXIP:ephemeralPort2.
