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Port 645 (pssc)

IANA assigns port 645 to pssc: PSSC.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
pssc TCP PSSC Egon Meier Engelen -
pssc UDP PSSC Egon Meier Engelen -

Check what is listening on port 645

Linux: is anything listening on TCP 645?
sudo ss -tlnp 'sport = :645'
Linux: UDP 645
sudo ss -ulnp 'sport = :645'
Linux / macOS: which process owns the port
sudo lsof -nP -i :645
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':645 '
Windows (Command Prompt)
netstat -ano | findstr :645
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 645 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 645
From Windows
Test-NetConnection HOST -Port 645
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 645

Block port 645 in the firewall

ufw
sudo ufw deny 645/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 645 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 645 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 645' -Direction Inbound -Protocol TCP -LocalPort 645 -Action Block
ufw
sudo ufw deny 645/udp
iptables
sudo iptables -A INPUT -p udp --dport 645 -j DROP
nftables
sudo nft add rule inet filter input udp dport 645 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 645' -Direction Inbound -Protocol UDP -LocalPort 645 -Action Block

Related ports

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