To access VNC a local vncserver must be started first and also a tunnel using SSH port forwarding must be established.
[See below](vnc.md#linux-example-of-creating-a-tunnel) for the details on SSH tunnels. In this example we use port 61.
[See below](vnc.md#linux-example-of-creating-a-tunnel) for the details on SSH tunnels. In this example we use display number 61.
You can find ports which are already occupied. Here you can see that ports " /usr/bin/Xvnc :79" and " /usr/bin/Xvnc :60" are occupied.
You can find display numbers which are already occupied on the login2. Here you can see that displays " /usr/bin/Xvnc :79" and " /usr/bin/Xvnc :60" are occupied.
```console
[username@login2 ~]$ps aux | grep Xvnc
...
...
@@ -44,7 +44,7 @@ Starting applications specified in /home/username/.vnc/xstartup
Log file is /home/username/.vnc/login2:1.log
```
Check if VNC server is started on the port (in this example 61):
Check if VNC server is started (in this example display number is 61):
The vncserver runs on port 5900 + display number. You get your port number simply as 5900 + display number (in this example 61), so the result is 5961.
To access the VNC server you have to create a tunnel between the login node using TCP **port 5961** and your machine using a free TCP port (for simplicity the very same, in this case).
To access the VNC server you have to create a tunnel between the login node using TCP **port 5961** and your machine using a free TCP port (for simplicity the very same, in this case). See examples for [Linux/Mac OS](#linuxmac-os-example-of-creating-a-tunnel) and [Windows](#windows-example-of-creating-a-tunnel).
!!! note
The tunnel must point to the same login node where you launched the VNC server, eg. login2. If you use just cluster-name.it4i.cz, the tunnel might point to a different node due to DNS round robin.