VNC Penetration Testing (Port 5901) - Hacking Articles
Virtual Network Computing - Wikipedia
Tools such as Shodan can find VNC running even on non-standard ports. Changing the port number isn’t a very good security measure. How to Allow VNC Ports. To access VNC on a public network (e.g. the Internet), you must forward the appropriate ports through your router/firewall. The exact steps are based on your specific router model. Port 5900 (tcp/udp) :: SpeedGuide
VNC server with UDP connection. Has anyone done it?
Port 5900 VNC TCP Blocked: Inbound Most commonly used with Apple remote desktop. Incoming connections are only permitted through approved entry points such as the campus VPN. Port 3389 TCP and UDP Microsoft Remote Desktop Protocol Blocked: Inbound.