Setting up SSH via our tunnel

The command to invoke on your end is simply

ssh -o TCPKeepAlive=no -o ServerAliveInterval=15 -nNT -R 8822:localhost:22 CUSTOMER@tunnel.soundflow.org

Replace CUSTOMER with the customer user name that we assigned you and enter the password we sent you.
Leave this command running for as long time as SoundFlow needs remote access to your server.
Important: Close this as soon as SoundFlow's done accessing the server.

SoundFlow will run these commands

This in a persistent tab to enable the tunnel:

ssh -o TCPKeepAlive=no -o ServerAliveInterval=15 -nNT -L 8822:localhost:8822 CUSTOMER@tunnel.soundflow.org

This to connect (REMOTEUSER being the remote username on the customer's server):

ssh -o TCPKeepAlive=no -o ServerAliveInterval=15 REMOTEUSER@localhost -p 8822

To copy from remote to local for example:

scp -o TCPKeepAlive=no -o ServerAliveInterval=15 -P 8822 -r REMOTEUSER@localhost:/home/laadmin/sffs ./sffscp

Source

https://www.sweetprocess.com/procedures/_AmM86Weq31FO0WDp5kRZFDBKRjB/ssh-tunnel-between-two-servers-behind-firewalls/

Computer B is the customer's server.
Computer A is SoundFlow's computer.
Computer C is our tunnel.