Connect to a server behind a NAT using mosh

If you’re not familiar with mosh it’s essentially SSH but with support for roaming and it works like a charm on slow connections. I wanted to access my server which is behind a NAT, but with the default config it was not straightforward to do so. When you first launch mosh, sshd is launched in the background then kills the connection, in order to circumvent that, edit the ssh daemon config file: /etc/ssh/sshd/config to add the port you want to connect to:


If you have SELinux enabled, you have to tell SELinux about this change.

semanage port -a -t ssh_port_t -p tcp #PORTNUMBER

After that, you need to forward the same port you’ll be listening to, to your router. Otherwise you won’t get any data back. You can now access your server with:

mosh --ssh="ssh -p #PORTNUMBER" -p #PORTNUMBER username@serveradress
Written on February 21, 2023