Create an SSH connection on your local computer that securely forwards to the localhost connection for VNC. You can do this via the terminal on Linux or macOS with the following command:

    ssh -L 5901:127.0.0.1:5901 -C -N -l testmachine_1 172.1.1.1

/etc/test$ ssh -L 5901:127.0.0.1:5901 -C -N -l testmachine_2 172.1.1.1
testmachine_2@172.1.1.1's password: