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Port 1990 (stun-p1)

IANA assigns port 1990 to stun-p1: cisco STUN Priority 1 port.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
stun-p1 TCP cisco STUN Priority 1 port - -
stun-p1 UDP cisco STUN Priority 1 port - -

Check what is listening on port 1990

Linux: is anything listening on TCP 1990?
sudo ss -tlnp 'sport = :1990'
Linux: UDP 1990
sudo ss -ulnp 'sport = :1990'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1990
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':1990 '
Windows (Command Prompt)
netstat -ano | findstr :1990
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1990 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 1990
From Windows
Test-NetConnection HOST -Port 1990
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1990

Block port 1990 in the firewall

ufw
sudo ufw deny 1990/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 1990 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 1990 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 1990' -Direction Inbound -Protocol TCP -LocalPort 1990 -Action Block
ufw
sudo ufw deny 1990/udp
iptables
sudo iptables -A INPUT -p udp --dport 1990 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1990 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1990' -Direction Inbound -Protocol UDP -LocalPort 1990 -Action Block

Related ports

1988tr-rsrb-p21989tr-rsrb-p3, mshnet1991stun-p21992stun-p3, ipsendmsg

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