Port 4374 (psi-ptt)

IANA assigns port 4374 to psi-ptt: PSI Push-to-Talk Protocol.

Registered (user) port, 1024-49151 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference

psi-ptt TCP PSI Push-to-Talk Protocol Frank B -

Registry dates for this port: registered 2008-07-17.

Linux: is anything listening on TCP 4374?

sudo ss -tlnp 'sport = :4374'

Linux / macOS: which process owns the port

sudo lsof -nP -i :4374

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':4374 '

Windows (Command Prompt)

netstat -ano | findstr :4374

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4374 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 4374

From Windows

Test-NetConnection HOST -Port 4374

ufw

sudo ufw deny 4374/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 4374 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 4374 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 4374' -Direction Inbound -Protocol TCP -LocalPort 4374 -Action Block

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