VNC through a firewall

  • Each X display (usually there is only one) has a number starting at :0 (the second would be :1).

  • The base port used for VNC is tcp port 5900.

  • The X display number (less the colon) is added to the port to determine the port used to access that display (so to contact display :1, one would use port 5901).

  • The port must be open on the server (remote computer, that is, the one to which you wish to connect to remotely control it).