I have two PCs in the same LAN: "A1" and "A2". There is another PC in a different LAN: "B". A TCP server is listening on machine "B", port 80. From machine "A1", I can connect successfully to machine "B". If I try to connect from machine "A2", I can see three outgoing TCP-SYN packets, but no response. The SYNs don't reach machine "B".
Windows firewall is turned off on machine "A2". If I start the TCP server on machine "A1", I'm able to connect to it from machine "A2".
What am I doing wrong? Thank you for your help.