Port 5800 (VNC over HTTP)

Java/HTML VNC viewer served over HTTP by some VNC servers (5800 + display).

Registered (user) port, 1024-49151 TCP Remote access Do not expose to the internet

What port 5800 is used for

Java/HTML VNC viewer served over HTTP by some VNC servers (5800 + display).

Do not expose to the internet. Same risks as 5900.

Port 5800 is in the registered range and has no IANA assignment. The usage above is unofficial but widespread.

Linux: is anything listening on TCP 5800?

sudo ss -tlnp 'sport = :5800'

Linux / macOS: which process owns the port

sudo lsof -nP -i :5800

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':5800 '

Windows (Command Prompt)

netstat -ano | findstr :5800

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 5800 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 5800

From Windows

Test-NetConnection HOST -Port 5800

ufw

sudo ufw deny 5800/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 5800 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 5800 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 5800' -Direction Inbound -Protocol TCP -LocalPort 5800 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.