CyberHunter
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// Other services

Port 3127: CTX Bridge Port

Port 3127 is assigned by IANA to ctx-bridge (CTX Bridge Port).

3127

How ctx-bridge works

Other services
client:3127ctx-bridgeresponse client:3127ctx-bridgeresponse

The client sends a request to port 3127 and the ctx-bridge 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 3127 dangerous?

We have no specific security note for port 3127. 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 3127

ServicePortTransportDescriptionReferenceUpdated
ctx-bridge 3127 TCP, UDP CTX Bridge Port - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 3127, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3127'      # process listening on 3127
sudo lsof -nP -i :3127

macOS

sudo lsof -nP -i :3127

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3127 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3127
netstat -ano | findstr :3127

From another machine

nmap -p 3127 -sV <host>
sudo nmap -sU -p 3127 <host>
nc -zv <host> 3127

Block it in the firewall

sudo ufw deny 3127/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3127" -Direction Inbound -LocalPort 3127 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3127 used for?

Port 3127 is assigned by IANA to ctx-bridge (CTX Bridge Port).

Is port 3127 TCP or UDP?

Port 3127 is registered for TCP and UDP.

Is it safe to open port 3127?

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 3127 is open?

On Linux run "ss -ltnup 'sport = :3127'", on macOS "lsof -nP -i :3127", and on Windows "netstat -ano | findstr :3127" to see the local process. From another machine, "nmap -p 3127 <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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