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Port 611 (npmp-gui)

IANA assigns port 611 to npmp-gui.

Well-known (system) port, 0-1023 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
npmp-gui TCP npmp-gui John Barnes -
npmp-gui UDP npmp-gui John Barnes -

Check what is listening on port 611

Linux: is anything listening on TCP 611?
sudo ss -tlnp 'sport = :611'
Linux: UDP 611
sudo ss -ulnp 'sport = :611'
Linux / macOS: which process owns the port
sudo lsof -nP -i :611
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':611 '
Windows (Command Prompt)
netstat -ano | findstr :611
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 611 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 611
From Windows
Test-NetConnection HOST -Port 611
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 611

Block port 611 in the firewall

ufw
sudo ufw deny 611/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 611 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 611 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 611' -Direction Inbound -Protocol TCP -LocalPort 611 -Action Block
ufw
sudo ufw deny 611/udp
iptables
sudo iptables -A INPUT -p udp --dport 611 -j DROP
nftables
sudo nft add rule inet filter input udp dport 611 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 611' -Direction Inbound -Protocol UDP -LocalPort 611 -Action Block

Related ports

609npmp-trap610npmp-local612hmmp-ind613hmmp-op

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