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Port 1994 (stun-port)

IANA assigns port 1994 to stun-port: cisco serial tunnel port.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
stun-port TCP cisco serial tunnel port - -
stun-port UDP cisco serial tunnel port - -

Check what is listening on port 1994

Linux: is anything listening on TCP 1994?
sudo ss -tlnp 'sport = :1994'
Linux: UDP 1994
sudo ss -ulnp 'sport = :1994'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1994
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':1994 '
Windows (Command Prompt)
netstat -ano | findstr :1994
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1994 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 1994
From Windows
Test-NetConnection HOST -Port 1994
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1994

Block port 1994 in the firewall

ufw
sudo ufw deny 1994/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 1994 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 1994 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 1994' -Direction Inbound -Protocol TCP -LocalPort 1994 -Action Block
ufw
sudo ufw deny 1994/udp
iptables
sudo iptables -A INPUT -p udp --dport 1994 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1994 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1994' -Direction Inbound -Protocol UDP -LocalPort 1994 -Action Block

Related ports

1992stun-p3, ipsendmsg1993snmp-tcp-port1995perf-port1996tr-rsrb-port

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.