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// Databases & caches

Port 4136: Classic Line Database Server Request

Port 4136 is assigned by IANA to cl-db-request (Classic Line Database Server Request).

4136

How cl-db-request works

Databases & caches
app:4136cl-db-request app:4136cl-db-request

The application sends a SQL query to the cl-db-request server on port 4136, which returns rows from its tables.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
Databases & caches
01 Security

Is port 4136 dangerous?

We have no specific security note for port 4136. Its risk depends on the program actually listening on it. General advice for databases & caches services:

  • Bind the service to localhost or a private network, never to a public address.
  • Enable authentication, use per-application accounts and require TLS.
  • Watch for exposed Docker ports: publish them on 127.0.0.1 only.
02 Registry

IANA registry entries for port 4136

ServicePortTransportDescriptionReferenceUpdated
cl-db-request 4136 TCP, UDP Classic Line Database Server Request - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 4136, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4136'      # process listening on 4136
sudo lsof -nP -i :4136

macOS

sudo lsof -nP -i :4136

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4136 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4136
netstat -ano | findstr :4136

From another machine

nmap -p 4136 -sV <host>
sudo nmap -sU -p 4136 <host>
nc -zv <host> 4136

Block it in the firewall

sudo ufw deny 4136/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4136" -Direction Inbound -LocalPort 4136 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4136 used for?

Port 4136 is assigned by IANA to cl-db-request (Classic Line Database Server Request).

Is port 4136 TCP or UDP?

Port 4136 is registered for TCP and UDP.

Is it safe to open port 4136?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Bind the service to localhost or a private network, never to a public address.

How do I check if port 4136 is open?

On Linux run "ss -ltnup 'sport = :4136'", on macOS "lsof -nP -i :4136", and on Windows "netstat -ano | findstr :4136" to see the local process. From another machine, "nmap -p 4136 <host>" shows whether it is reachable.

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