Port 6252 (tl1-ssh)

IANA assigns port 6252 to tl1-ssh: TL1 over SSH.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference

tl1-ssh TCP TL1 over SSH Jim Humphreys -

tl1-ssh UDP TL1 over SSH Jim Humphreys -

Registry dates for this port: registered 2008-01-25.

Linux: is anything listening on TCP 6252?

sudo ss -tlnp 'sport = :6252'

Linux: UDP 6252

sudo ss -ulnp 'sport = :6252'

Linux / macOS: which process owns the port

sudo lsof -nP -i :6252

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':6252 '

Windows (Command Prompt)

netstat -ano | findstr :6252

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 6252 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 6252

From Windows

Test-NetConnection HOST -Port 6252

UDP probe (no reply does not prove it is closed)

nc -vzu -w 5 HOST 6252

ufw

sudo ufw deny 6252/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 6252 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 6252 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 6252' -Direction Inbound -Protocol TCP -LocalPort 6252 -Action Block

ufw

sudo ufw deny 6252/udp

iptables

sudo iptables -A INPUT -p udp --dport 6252 -j DROP

nftables

sudo nft add rule inet filter input udp dport 6252 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block UDP 6252' -Direction Inbound -Protocol UDP -LocalPort 6252 -Action Block

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