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Port 5991 (nuxsl)

IANA assigns port 5991 to nuxsl: NUXSL.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
nuxsl TCP NUXSL Kai Kretschmann -
nuxsl UDP NUXSL Kai Kretschmann -

Registry dates for this port: registered 2002-03.

Check what is listening on port 5991

Linux: is anything listening on TCP 5991?
sudo ss -tlnp 'sport = :5991'
Linux: UDP 5991
sudo ss -ulnp 'sport = :5991'
Linux / macOS: which process owns the port
sudo lsof -nP -i :5991
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':5991 '
Windows (Command Prompt)
netstat -ano | findstr :5991
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 5991 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 5991
From Windows
Test-NetConnection HOST -Port 5991
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 5991

Block port 5991 in the firewall

ufw
sudo ufw deny 5991/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 5991 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 5991 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 5991' -Direction Inbound -Protocol TCP -LocalPort 5991 -Action Block
ufw
sudo ufw deny 5991/udp
iptables
sudo iptables -A INPUT -p udp --dport 5991 -j DROP
nftables
sudo nft add rule inet filter input udp dport 5991 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 5991' -Direction Inbound -Protocol UDP -LocalPort 5991 -Action Block

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5989wbem-https5990wbem-exp-https5992consul-insight5993cim-rs

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