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Port 3540 (pnrp-port)

IANA assigns port 3540 to pnrp-port: PNRP User Port.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
pnrp-port TCP PNRP User Port Igor Kostic -
pnrp-port UDP PNRP User Port Igor Kostic -

Registry dates for this port: registered 2002-07.

Check what is listening on port 3540

Linux: is anything listening on TCP 3540?
sudo ss -tlnp 'sport = :3540'
Linux: UDP 3540
sudo ss -ulnp 'sport = :3540'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3540
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3540 '
Windows (Command Prompt)
netstat -ano | findstr :3540
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3540 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3540
From Windows
Test-NetConnection HOST -Port 3540
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3540

Block port 3540 in the firewall

ufw
sudo ufw deny 3540/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3540 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3540 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3540' -Direction Inbound -Protocol TCP -LocalPort 3540 -Action Block
ufw
sudo ufw deny 3540/udp
iptables
sudo iptables -A INPUT -p udp --dport 3540 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3540 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3540' -Direction Inbound -Protocol UDP -LocalPort 3540 -Action Block

Related ports

3538ibm-diradm3539ibm-diradm-ssl3541voispeed-port3542hacl-monitor

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