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Port 556 (remotefs)

IANA assigns port 556 to remotefs: rfs server.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
remotefs TCP rfs server - -
remotefs UDP rfs server - -

Check what is listening on port 556

Linux: is anything listening on TCP 556?
sudo ss -tlnp 'sport = :556'
Linux: UDP 556
sudo ss -ulnp 'sport = :556'
Linux / macOS: which process owns the port
sudo lsof -nP -i :556
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':556 '
Windows (Command Prompt)
netstat -ano | findstr :556
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 556 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 556
From Windows
Test-NetConnection HOST -Port 556
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 556

Block port 556 in the firewall

ufw
sudo ufw deny 556/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 556 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 556 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 556' -Direction Inbound -Protocol TCP -LocalPort 556 -Action Block
ufw
sudo ufw deny 556/udp
iptables
sudo iptables -A INPUT -p udp --dport 556 -j DROP
nftables
sudo nft add rule inet filter input udp dport 556 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 556' -Direction Inbound -Protocol UDP -LocalPort 556 -Action Block

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553pirp554RTSP557openvms-sysipc558sdnskmp

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