CyberHunter
Local dataset, no network
// Other services

Port 4139: Imperfect Networks Server

Port 4139 is assigned by IANA to thrtx (Imperfect Networks Server).

4139

How thrtx works

Other services
client:4139thrtxresponse client:4139thrtxresponse

The client sends a request to port 4139 and the thrtx 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 4139 dangerous?

We have no specific security note for port 4139. 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 4139

ServicePortTransportDescriptionReferenceUpdated
thrtx 4139 TCP, UDP Imperfect Networks Server - 2006-02

// source: IANA service name and port number registry

03 Check it

Which program uses port 4139, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4139'      # process listening on 4139
sudo lsof -nP -i :4139

macOS

sudo lsof -nP -i :4139

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4139 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4139
netstat -ano | findstr :4139

From another machine

nmap -p 4139 -sV <host>
sudo nmap -sU -p 4139 <host>
nc -zv <host> 4139

Block it in the firewall

sudo ufw deny 4139/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4139" -Direction Inbound -LocalPort 4139 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4139 used for?

Port 4139 is assigned by IANA to thrtx (Imperfect Networks Server).

Is port 4139 TCP or UDP?

Port 4139 is registered for TCP and UDP.

Is it safe to open port 4139?

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 4139 is open?

On Linux run "ss -ltnup 'sport = :4139'", on macOS "lsof -nP -i :4139", and on Windows "netstat -ano | findstr :4139" to see the local process. From another machine, "nmap -p 4139 <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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