HTTPfy

Port 4137 (cl-db-remote)

IANA assigns port 4137 to cl-db-remote: Classic Line Database Server Remote.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
cl-db-remote TCP Classic Line Database Server Remote Arno Kirmeir -
cl-db-remote UDP Classic Line Database Server Remote Arno Kirmeir -

Registry dates for this port: registered 2007-01.

Check what is listening on port 4137

Linux: is anything listening on TCP 4137?
sudo ss -tlnp 'sport = :4137'
Linux: UDP 4137
sudo ss -ulnp 'sport = :4137'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4137
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':4137 '
Windows (Command Prompt)
netstat -ano | findstr :4137
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4137 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 4137
From Windows
Test-NetConnection HOST -Port 4137
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 4137

Block port 4137 in the firewall

ufw
sudo ufw deny 4137/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 4137 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 4137 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 4137' -Direction Inbound -Protocol TCP -LocalPort 4137 -Action Block
ufw
sudo ufw deny 4137/udp
iptables
sudo iptables -A INPUT -p udp --dport 4137 -j DROP
nftables
sudo nft add rule inet filter input udp dport 4137 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 4137' -Direction Inbound -Protocol UDP -LocalPort 4137 -Action Block

Related ports

4135cl-db-attach4136cl-db-request4138nettest4139thrtx

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