Thanks for providing your solution. That is odd, I was pretty sure that it should also work with port 2 (although I'm normally only using port 1).
I did some research and found this thread. Check the last post. This does not explain why it didn't work with port 2 but it is an intersting statement.
Good thread!
At the begining I was not able even over port 1 because the subnet mask was 255.255.255.128 on the robot side and I was configuring my laptop with the ip xxx.xxx.xxx.250. I changed to xxx.xxx.xxx.55 that was a spare ip and everything worked!