Port 9640 (pqsflows)

IANA assigns port 9640 to pqsflows: ProQueSys Flows Service.

Registered (user) port, 1024-49151 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference

pqsflows TCP ProQueSys Flows Service Sarene Caiazza -

Registry dates for this port: registered 2010-04-27.

Linux: is anything listening on TCP 9640?

sudo ss -tlnp 'sport = :9640'

Linux / macOS: which process owns the port

sudo lsof -nP -i :9640

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':9640 '

Windows (Command Prompt)

netstat -ano | findstr :9640

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 9640 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 9640

From Windows

Test-NetConnection HOST -Port 9640

ufw

sudo ufw deny 9640/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 9640 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 9640 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 9640' -Direction Inbound -Protocol TCP -LocalPort 9640 -Action Block

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