TCP: Server sends [RST, ACK] immediately after receiving [SYN] from Client

linux tcp nio redhat

RST, ACK means the port is closed. You sure Host_B is listening on the right IP/interface?

Also check your firewall for a -j REJECT --reject-with tcp-reset

linux tcp nio redhat

It happened to me because I did not set sockaddr_in.sin_family to AF_INET, in the server c++ program.

CodeHunter