[icq-devel] ICQ File Transfer in DC mode

Husam Khater hkhater at gmx.net
Wed Jun 25 20:57:42 CEST 2003

I'm investigating ICQ file transfer, and I notices the following:

1- Version 9 client transferring to Version 8 client:
 In this case some kind of handshake (through the ICQ server port 5190) takes place, and the port to be opened for direct connection is communicated through this handshake. After that the DC session gets opened using that port.

2- Version 8 client transferring to Version 8 client:
The first transfer will follow (1), but the subsequent transfers open direct connections (with different ports used each time) after this some handshake (in DC mode) takes place, followed by the actual transfer.

My question is about the second case:
 How can the receiving agent determine which port will be opened for DC handshake?


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