VNC is a protocol used to connect remote systems with GUI. It is especially popular in Linux world but supports other platforms like Microsoft and MacOS. The default port numbering for multiple VNC services can be tricky for new comers. In this tutorial we will look port and numbering about VNC.

Default Port 5900

The default port for VNC server is TCP 5900 . This port can be changed if we need. Especially if this VNC service is open to the internet or insecure networks changing default port will make our system more secure.

New Desktop Session Port

We can create new desktop sessions with a single VNC daemon or service. We can configure new desktop and listen new TCP port for the new sessions. Newly added ports will get BASE PORT NUMBER +1 . Which means if BASE PORT NUMBER is 5900 new desktop session will be 5901. This will increment one by one if we add new desktop sessions.

VNC Web Interface Port 5800

VNC can be generally used with desktop client applications. But some VNC server software provides web based client which do not needs VNC desktop client. Web VNC clients generally uses TCP 5800.

Check Default and Other Ports

We can check wheter remote VNC server port is open with telnet . In this example we will check remote system 10.0.2.27 port 5900 is open.

$ telnet 10.0.2.27 5900

We can see that telnet is connected successfully and remote VNC server provided some response like RFB 003.008 which means remote port is a VNC server and up.