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// Other services

Port 127: Locus PC-Interface Conn Server

Port 127 is assigned by IANA to locus-con (Locus PC-Interface Conn Server).

127

How locus-con works

Other services
client:127locus-conresponse client:127locus-conresponse

The client sends a request to port 127 and the locus-con 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
Well-known (0-1023)
Category
Other services
01 Security

Is port 127 dangerous?

We have no specific security note for port 127. 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 127

ServicePortTransportDescriptionReferenceUpdated
locus-con 127 TCP, UDP Locus PC-Interface Conn Server - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 127, and is it reachable?

Linux

sudo ss -ltnup 'sport = :127'      # process listening on 127
sudo lsof -nP -i :127

macOS

sudo lsof -nP -i :127

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 127 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 127
netstat -ano | findstr :127

From another machine

nmap -p 127 -sV <host>
sudo nmap -sU -p 127 <host>
nc -zv <host> 127

Block it in the firewall

sudo ufw deny 127/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 127" -Direction Inbound -LocalPort 127 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 127 used for?

Port 127 is assigned by IANA to locus-con (Locus PC-Interface Conn Server).

Is port 127 TCP or UDP?

Port 127 is registered for TCP and UDP.

Is it safe to open port 127?

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 127 is open?

On Linux run "ss -ltnup 'sport = :127'", on macOS "lsof -nP -i :127", and on Windows "netstat -ano | findstr :127" to see the local process. From another machine, "nmap -p 127 <host>" shows whether it is reachable.

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