If you look at the config_db.php file, you'll see the connection information and company prefix (tbpref) for each company. As apmuthu pointed out, you could use localhost and a forwarded port to securely access a server on a host using SSH to set up port forwarding. You could also just set the host and port to directly access the remote host.

For a SSH Remote Tunnel visit here, here, here and for CLI visit here.

If you are using plain VPS without cpanels. try with the server ip address instead of the "localhost".