CyberHunter
Local dataset, no network
// Other services

Port 3733: Multipuesto Msg Port

Port 3733 is assigned by IANA to multip-msg (Multipuesto Msg Port).

3733

How multip-msg works

Other services
client:3733multip-msgresponse client:3733multip-msgresponse

The client sends a request to port 3733 and the multip-msg 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 3733 dangerous?

We have no specific security note for port 3733. 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 3733

ServicePortTransportDescriptionReferenceUpdated
multip-msg 3733 TCP, UDP Multipuesto Msg Port - 2003-04

// source: IANA service name and port number registry

03 Check it

Which program uses port 3733, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3733'      # process listening on 3733
sudo lsof -nP -i :3733

macOS

sudo lsof -nP -i :3733

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3733 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3733
netstat -ano | findstr :3733

From another machine

nmap -p 3733 -sV <host>
sudo nmap -sU -p 3733 <host>
nc -zv <host> 3733

Block it in the firewall

sudo ufw deny 3733/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3733" -Direction Inbound -LocalPort 3733 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3733 used for?

Port 3733 is assigned by IANA to multip-msg (Multipuesto Msg Port).

Is port 3733 TCP or UDP?

Port 3733 is registered for TCP and UDP.

Is it safe to open port 3733?

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 3733 is open?

On Linux run "ss -ltnup 'sport = :3733'", on macOS "lsof -nP -i :3733", and on Windows "netstat -ano | findstr :3733" to see the local process. From another machine, "nmap -p 3733 <host>" shows whether it is reachable.

05 Related
:4444 Metasploit default / krb524 tcp · udp · high risk :31337 Back Orifice / elite tcp · udp · high risk :1 TCP Port Service Multiplexer tcp · udp :5 Remote Job Entry tcp · udp :9 Discard tcp · udp · sctp · dccp :11 Active Users tcp · udp :17 Quote of the Day tcp · udp :18 Message Send Protocol (historic) tcp · udp

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