Refer to: http://blog.trackets.com/2014/05/17/ssh-tunnel-local-and-remote-port-forwarding-explained-with-examples.html
You are blocked from making connection to a port, say, 6666. Luckily, you still can connect to a remote server via port 22 (ssh).
We can do SSH tunneling to get through the firewall via port 22 (which is not blocked here) and use a pivotal server to connect to the port 6666 relaying all the data back to us behind the firewall.
ssh -L <local_port>:<target_host>:<target_port> <pivotal_host>
In this case, it might be:
ssh -L 22:targethost.com:6666 [email protected]
Then, you can ssh, via the pivotalhost.com, to the targethost.com using
ssh [email protected] [-p 22]
Note : use
localhost here because ssh has bound the port 22 on this machine.