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Port 655 (tinc)

IANA assigns port 655 to tinc: TINC.

Well-known (system) port, 0-1023 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
tinc TCP TINC Ivo Timmermans -
tinc UDP TINC Ivo Timmermans -

Check what is listening on port 655

Linux: is anything listening on TCP 655?
sudo ss -tlnp 'sport = :655'
Linux: UDP 655
sudo ss -ulnp 'sport = :655'
Linux / macOS: which process owns the port
sudo lsof -nP -i :655
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':655 '
Windows (Command Prompt)
netstat -ano | findstr :655
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 655 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 655
From Windows
Test-NetConnection HOST -Port 655
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 655

Block port 655 in the firewall

ufw
sudo ufw deny 655/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 655 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 655 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 655' -Direction Inbound -Protocol TCP -LocalPort 655 -Action Block
ufw
sudo ufw deny 655/udp
iptables
sudo iptables -A INPUT -p udp --dport 655 -j DROP
nftables
sudo nft add rule inet filter input udp dport 655 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 655' -Direction Inbound -Protocol UDP -LocalPort 655 -Action Block

Related ports

653repscmd654aodv656spmp657rmc

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.