Disconnects you from the session you are connected to.
{"msg":"disconnect","instance_guid":"my_session_id_here"}

Once you are disconnected the clients connected to that session id will receive:
{"MSG":"Disconnected","SocketID":0}

If they are the instance owner then who ever is first on the list will be the new instance owner:
{"MSG":"update_instance_owner","SocketID":1}

If the session is a server only then everyone is kicked:
{"MSG":"ServerDisconnected"}