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Port 557 (openvms-sysipc)

IANA assigns port 557 to openvms-sysipc.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
openvms-sysipc TCP openvms-sysipc Alan Potter -
openvms-sysipc UDP openvms-sysipc Alan Potter -

Check what is listening on port 557

Linux: is anything listening on TCP 557?
sudo ss -tlnp 'sport = :557'
Linux: UDP 557
sudo ss -ulnp 'sport = :557'
Linux / macOS: which process owns the port
sudo lsof -nP -i :557
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':557 '
Windows (Command Prompt)
netstat -ano | findstr :557
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 557 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 557
From Windows
Test-NetConnection HOST -Port 557
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 557

Block port 557 in the firewall

ufw
sudo ufw deny 557/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 557 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 557 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 557' -Direction Inbound -Protocol TCP -LocalPort 557 -Action Block
ufw
sudo ufw deny 557/udp
iptables
sudo iptables -A INPUT -p udp --dport 557 -j DROP
nftables
sudo nft add rule inet filter input udp dport 557 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 557' -Direction Inbound -Protocol UDP -LocalPort 557 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.