Communication between qnx4 and qnx6

Hi, if I want to have an application under qnx6 to communicate with an application under qnx4 using tcp/ip (like an instant messenger) wich is the best way to implement this?
I don’t have too much experience in this…

This is not really a QNX 4 or QNX 6 question, but rather a TCP/IP question.
You have two main protocol choices TCP or UDP. Then there is a question of architecture. Do you want the two PC’s to communicate directly, or through a third intermediary as AIM seems to do? If the answer is the former, how do the two PC’s find each other? Is the communication asymetric, in which case one PC is a client and the other a server, or is it symetric?