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// Other services

Port 3311: MCNS Tel Ret

Port 3311 is assigned by IANA to mcns-tel-ret (MCNS Tel Ret).

3311

How mcns-tel-ret works

Other services
client:3311mcns-tel-retresponse client:3311mcns-tel-retresponse

The client sends a request to port 3311 and the mcns-tel-ret service answers.

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
Other services
01 Security

Is port 3311 dangerous?

We have no specific security note for port 3311. 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 3311

ServicePortTransportDescriptionReferenceUpdated
mcns-tel-ret 3311 TCP, UDP MCNS Tel Ret - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 3311, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3311'      # process listening on 3311
sudo lsof -nP -i :3311

macOS

sudo lsof -nP -i :3311

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3311 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3311
netstat -ano | findstr :3311

From another machine

nmap -p 3311 -sV <host>
sudo nmap -sU -p 3311 <host>
nc -zv <host> 3311

Block it in the firewall

sudo ufw deny 3311/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3311" -Direction Inbound -LocalPort 3311 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3311 used for?

Port 3311 is assigned by IANA to mcns-tel-ret (MCNS Tel Ret).

Is port 3311 TCP or UDP?

Port 3311 is registered for TCP and UDP.

Is it safe to open port 3311?

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 3311 is open?

On Linux run "ss -ltnup 'sport = :3311'", on macOS "lsof -nP -i :3311", and on Windows "netstat -ano | findstr :3311" to see the local process. From another machine, "nmap -p 3311 <host>" shows whether it is reachable.

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