A <= ping => B => OK A <= TCP => B => FAILS

Hi ng,

i've two linux systems (A and B).
I can successfully ping A from B and vice versa.

A simple TCP-Connection from A to B is failing.
I'm using the following TCP SimpleServer and SimpleClient Examples:

The TCP/IP stack should be ok, since a TCP connection with this program
is working from A<=>A and B<=>B and from A<=>C

Does anyone has a hint what could be the problem?