Port 28001 (pqsp)

IANA assigns port 28001 to pqsp: PQ Service.

Registered (user) port, 1024-49151 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference

pqsp TCP PQ Service Peter Laschtowitz -

Registry dates for this port: registered 2009-09-15.

Linux: is anything listening on TCP 28001?

sudo ss -tlnp 'sport = :28001'

Linux / macOS: which process owns the port

sudo lsof -nP -i :28001

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':28001 '

Windows (Command Prompt)

netstat -ano | findstr :28001

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 28001 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 28001

From Windows

Test-NetConnection HOST -Port 28001

ufw

sudo ufw deny 28001/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 28001 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 28001 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 28001' -Direction Inbound -Protocol TCP -LocalPort 28001 -Action Block

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