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Port 6657 (palcom-disc)

IANA assigns port 6657 to palcom-disc: PalCom Discovery.

Registered (user) port, 1024-49151 UDP

Port 6657 is normally used over UDP; the checker tests TCP only, so a "filtered" result does not mean the UDP service is down.

IANA assignment

Service nameProtoDescriptionAssigneeReference
palcom-disc UDP PalCom Discovery Boris Magnusson -

Registry dates for this port: registered 2010-12-06.

Check what is listening on port 6657

Linux: UDP 6657
sudo ss -ulnp 'sport = :6657'
Linux / macOS: which process owns the port
sudo lsof -nP -i :6657
Windows (Command Prompt)
netstat -ano | findstr :6657
Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 6657

Test it from outside

UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 6657

Block port 6657 in the firewall

ufw
sudo ufw deny 6657/udp
iptables
sudo iptables -A INPUT -p udp --dport 6657 -j DROP
nftables
sudo nft add rule inet filter input udp dport 6657 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 6657' -Direction Inbound -Protocol UDP -LocalPort 6657 -Action Block

Related ports

6655pcs-sf-ui-man6656emgmsg6665ircu6666ircu

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