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Port 2991 (wkstn-mon)

IANA assigns port 2991 to wkstn-mon: WKSTN-MON.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
wkstn-mon TCP WKSTN-MON William David -
wkstn-mon UDP WKSTN-MON William David -

Check what is listening on port 2991

Linux: is anything listening on TCP 2991?
sudo ss -tlnp 'sport = :2991'
Linux: UDP 2991
sudo ss -ulnp 'sport = :2991'
Linux / macOS: which process owns the port
sudo lsof -nP -i :2991
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':2991 '
Windows (Command Prompt)
netstat -ano | findstr :2991
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 2991 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 2991
From Windows
Test-NetConnection HOST -Port 2991
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 2991

Block port 2991 in the firewall

ufw
sudo ufw deny 2991/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 2991 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 2991 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 2991' -Direction Inbound -Protocol TCP -LocalPort 2991 -Action Block
ufw
sudo ufw deny 2991/udp
iptables
sudo iptables -A INPUT -p udp --dport 2991 -j DROP
nftables
sudo nft add rule inet filter input udp dport 2991 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 2991' -Direction Inbound -Protocol UDP -LocalPort 2991 -Action Block

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