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// Other services

Port 7901: TNOS Service Protocol

Port 7901 is assigned by IANA to tnos-sp (TNOS Service Protocol).

7901

How tnos-sp works

Other services
client:7901tnos-spresponse client:7901tnos-spresponse

The client sends a request to port 7901 and the tnos-sp 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 7901 dangerous?

We have no specific security note for port 7901. 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 7901

ServicePortTransportDescriptionReferenceUpdated
tnos-sp 7901 TCP, UDP TNOS Service Protocol - 2005-08

// source: IANA service name and port number registry

03 Check it

Which program uses port 7901, and is it reachable?

Linux

sudo ss -ltnup 'sport = :7901'      # process listening on 7901
sudo lsof -nP -i :7901

macOS

sudo lsof -nP -i :7901

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 7901 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 7901
netstat -ano | findstr :7901

From another machine

nmap -p 7901 -sV <host>
sudo nmap -sU -p 7901 <host>
nc -zv <host> 7901

Block it in the firewall

sudo ufw deny 7901/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 7901" -Direction Inbound -LocalPort 7901 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 7901 used for?

Port 7901 is assigned by IANA to tnos-sp (TNOS Service Protocol).

Is port 7901 TCP or UDP?

Port 7901 is registered for TCP and UDP.

Is it safe to open port 7901?

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 7901 is open?

On Linux run "ss -ltnup 'sport = :7901'", on macOS "lsof -nP -i :7901", and on Windows "netstat -ano | findstr :7901" to see the local process. From another machine, "nmap -p 7901 <host>" shows whether it is reachable.

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