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// Other services

Port 4335: NETCONF Call Home (TLS)

Port 4335 is assigned by IANA to netconf-ch-tls (NETCONF Call Home (TLS)).

4335

How netconf-ch-tls works

Other services
client:4335netconf-ch-tlsresponse client:4335netconf-ch-tlsresponse

The client sends a request to port 4335 and the netconf-ch-tls service answers.

Transport
TCP
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
Other services
01 Security

Is port 4335 dangerous?

We have no specific security note for port 4335. Its risk depends on the program actually listening on it. General advice for other services services:

  • Close the port if nothing on the host needs it.
  • Identify the process that listens on it (commands below) before opening it in a firewall.
  • Expose a service only to the networks that use it.
02 Registry

IANA registry entries for port 4335

ServicePortTransportDescriptionReferenceUpdated
netconf-ch-tls 4335 TCP NETCONF Call Home (TLS) RFC 8071 2016-01-12
-4335-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 4335, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4335'      # process listening on 4335
sudo lsof -nP -i :4335

macOS

sudo lsof -nP -i :4335

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4335 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4335
netstat -ano | findstr :4335

From another machine

nmap -p 4335 -sV <host>
nc -zv <host> 4335

Block it in the firewall

sudo ufw deny 4335/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4335" -Direction Inbound -LocalPort 4335 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4335 used for?

Port 4335 is assigned by IANA to netconf-ch-tls (NETCONF Call Home (TLS)).

Is port 4335 TCP or UDP?

Port 4335 is registered for TCP.

Is it safe to open port 4335?

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. Close the port if nothing on the host needs it.

How do I check if port 4335 is open?

On Linux run "ss -ltnup 'sport = :4335'", on macOS "lsof -nP -i :4335", and on Windows "netstat -ano | findstr :4335" to see the local process. From another machine, "nmap -p 4335 <host>" shows whether it is reachable.

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