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Port 451 (sfs-smp-net)

IANA assigns port 451 to sfs-smp-net: Cray Network Semaphore server.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
sfs-smp-net TCP Cray Network Semaphore server - -
sfs-smp-net UDP Cray Network Semaphore server - -

Check what is listening on port 451

Linux: is anything listening on TCP 451?
sudo ss -tlnp 'sport = :451'
Linux: UDP 451
sudo ss -ulnp 'sport = :451'
Linux / macOS: which process owns the port
sudo lsof -nP -i :451
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':451 '
Windows (Command Prompt)
netstat -ano | findstr :451
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 451 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 451
From Windows
Test-NetConnection HOST -Port 451
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 451

Block port 451 in the firewall

ufw
sudo ufw deny 451/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 451 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 451 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 451' -Direction Inbound -Protocol TCP -LocalPort 451 -Action Block
ufw
sudo ufw deny 451/udp
iptables
sudo iptables -A INPUT -p udp --dport 451 -j DROP
nftables
sudo nft add rule inet filter input udp dport 451 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 451' -Direction Inbound -Protocol UDP -LocalPort 451 -Action Block

Related ports

449as-servermap450tserver452sfs-config453creativeserver

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