localhost = Host server to connect to (the remote PC, same as 127.0.0.1)
5901 = Port on the remote host (forwarded from the client PC)
SSH Local and Remote Port Forwarding with VNC
Local port forwarding – A port from the client PC is forwarded to the remote PC. A connection to this port enables data to be sent bidirectionally over the SSH connection between the client and remote PC.
SSH: Dynamic Port Forwarding
# Listen on local port 8080 and forward incoming traffic to REMOT_HOST:PORT via SSH_SERVER
# Scenario: access a host that's being blocked by a firewall via SSH_SERVER;