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Port 4043 (nirp)

IANA assigns port 4043 to nirp: Neighbour Identity Resolution.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
nirp TCP Neighbour Identity Resolution - -
nirp UDP Neighbour Identity Resolution - -

Check what is listening on port 4043

Linux: is anything listening on TCP 4043?
sudo ss -tlnp 'sport = :4043'
Linux: UDP 4043
sudo ss -ulnp 'sport = :4043'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4043
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':4043 '
Windows (Command Prompt)
netstat -ano | findstr :4043
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4043 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 4043
From Windows
Test-NetConnection HOST -Port 4043
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 4043

Block port 4043 in the firewall

ufw
sudo ufw deny 4043/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 4043 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 4043 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 4043' -Direction Inbound -Protocol TCP -LocalPort 4043 -Action Block
ufw
sudo ufw deny 4043/udp
iptables
sudo iptables -A INPUT -p udp --dport 4043 -j DROP
nftables
sudo nft add rule inet filter input udp dport 4043 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 4043' -Direction Inbound -Protocol UDP -LocalPort 4043 -Action Block

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