After you have logged in to the gateway using your SSH2 client, your SSH2 client will be sent periodic ClientAlive messages by the SSH2 server.
The ClientAlive message, sent over the encrypted channel, causes your client to respond over the same channel. This regular heartbeat is how we make sure that you are not replaced by another user after you log in. As long as your client responds to the ClientAlive messages, we know your heart is still beating, and you are still you.
If your client stops responding, after a minute you will be assumed to have either shut down, closed your SSH2 client, or moved out of range of the network. The next user of your IP address will then need to log in as him- or herself before using the network.
Finally, when you want to log off, you can do so by typing 'logout' in ( or just closing) the SSH2 client window you used for authenticating.