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// Databases & caches

Port 4135: Classic Line Database Server Attach

Port 4135 is assigned by IANA to cl-db-attach (Classic Line Database Server Attach).

4135

How cl-db-attach works

Databases & caches
app:4135cl-db-attach app:4135cl-db-attach

The application sends a SQL query to the cl-db-attach server on port 4135, 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 4135 dangerous?

We have no specific security note for port 4135. 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 4135

ServicePortTransportDescriptionReferenceUpdated
cl-db-attach 4135 TCP, UDP Classic Line Database Server Attach - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 4135, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4135'      # process listening on 4135
sudo lsof -nP -i :4135

macOS

sudo lsof -nP -i :4135

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4135 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4135
netstat -ano | findstr :4135

From another machine

nmap -p 4135 -sV <host>
sudo nmap -sU -p 4135 <host>
nc -zv <host> 4135

Block it in the firewall

sudo ufw deny 4135/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4135" -Direction Inbound -LocalPort 4135 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4135 used for?

Port 4135 is assigned by IANA to cl-db-attach (Classic Line Database Server Attach).

Is port 4135 TCP or UDP?

Port 4135 is registered for TCP and UDP.

Is it safe to open port 4135?

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 4135 is open?

On Linux run "ss -ltnup 'sport = :4135'", on macOS "lsof -nP -i :4135", and on Windows "netstat -ano | findstr :4135" to see the local process. From another machine, "nmap -p 4135 <host>" shows whether it is reachable.

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