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Port 542 (commerce)

IANA assigns port 542 to commerce.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
commerce TCP commerce Randy Epstein -
commerce UDP commerce Randy Epstein -

Check what is listening on port 542

Linux: is anything listening on TCP 542?
sudo ss -tlnp 'sport = :542'
Linux: UDP 542
sudo ss -ulnp 'sport = :542'
Linux / macOS: which process owns the port
sudo lsof -nP -i :542
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':542 '
Windows (Command Prompt)
netstat -ano | findstr :542
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 542 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 542
From Windows
Test-NetConnection HOST -Port 542
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 542

Block port 542 in the firewall

ufw
sudo ufw deny 542/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 542 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 542 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 542' -Direction Inbound -Protocol TCP -LocalPort 542 -Action Block
ufw
sudo ufw deny 542/udp
iptables
sudo iptables -A INPUT -p udp --dport 542 -j DROP
nftables
sudo nft add rule inet filter input udp dport 542 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 542' -Direction Inbound -Protocol UDP -LocalPort 542 -Action Block

Related ports

540uucp541uucp-rlogin544kshell545appleqtcsrvr

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