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Port 6201 (thermo-calc)

IANA assigns port 6201 to thermo-calc: Management of service nodes in a processing grid for thermodynamic calculations.

Registered (user) port, 1024-49151 UDP

Port 6201 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
thermo-calc UDP Management of service nodes in a processing grid for thermodynamic calculations Thermo-Calc Software -

Registry dates for this port: registered 2012-06-28.

Check what is listening on port 6201

Linux: UDP 6201
sudo ss -ulnp 'sport = :6201'
Linux / macOS: which process owns the port
sudo lsof -nP -i :6201
Windows (Command Prompt)
netstat -ano | findstr :6201
Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 6201

Test it from outside

UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 6201

Block port 6201 in the firewall

ufw
sudo ufw deny 6201/udp
iptables
sudo iptables -A INPUT -p udp --dport 6201 -j DROP
nftables
sudo nft add rule inet filter input udp dport 6201 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 6201' -Direction Inbound -Protocol UDP -LocalPort 6201 -Action Block

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