SSH to a machine behind firewall. On a related note, LocalCommand and RemoteCommand are also handy in some cases, e.g., LocalCommand osascript -e "tell application \"Terminal\" to set current settings of window 1 to settings set \"ssh\"" to change Apple Terminal theme when ssh’ing on a remomte machine, or RemoteCommand tmux new -A -s remote -n main to start Tmux right when connecting to a remote server.