One of our DBs is behind firewall.
I could not use it through its natural port 1521.
I also know the same machine is accessible through the SSH port ( 22)
My friend showed me BitVise SSH Client, so that by tunneling through the SSH port , I accessed the invulnerable 1521 port and used my favorite Sql Developer tool.
My question is , how do you tunnel some data through the SSH port, what is the mechanics ? I.e. is there some SSH command like, "after successful login pass the data as is to the given port"
You need to use a SSH client to connect to the Bitvise SSH server. Bitvise also has a client product called Bitvise Tunnelier that you can configure to use port forwarding. You would configure Tunnelier to listen for and forward a specific port (the SQL connection in your case). Then, you would configure your SQL Dev Tool to connect to localhost: and connect.
More information about Bitvise and port forwarding: https://www.bitvise.com/port-forwarding
This link will show you how to use Port Forwarding with Remote Desktop, but you can adapt it to use it for SQL, etc: https://www.bitvise.com/remote-desktop