Port 5900 supports VNC and rfb (UDP reference coverage) across distinct transports. Review each protocol before writing firewall or monitoring policy.
First display endpoint in the common VNC remote-framebuffer range.
VNC endpoints in environments where this service is explicitly configured.
Client to server
Do not expose directly to the internet; tunnel through a VPN or SSH and require strong authentication.
rfb (UDP reference coverage) is documented as a network service convention for port 5900 over UDP.
Use this reference entry when identifying or validating systems documented to use 5900/UDP.
Varies
Confirm the listening process and current vendor documentation before permitting traffic; a listed convention does not prove the active service or its security posture.