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// Other services

Port 5581: T-Mobile SMS Protocol Message 1

Port 5581 is assigned by IANA to tmosms1 (T-Mobile SMS Protocol Message 1).

5581

How tmosms1 works

Other services
client:5581tmosms1response client:5581tmosms1response

The client sends a request to port 5581 and the tmosms1 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 5581 dangerous?

We have no specific security note for port 5581. 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 5581

ServicePortTransportDescriptionReferenceUpdated
tmosms1 5581 TCP, UDP T-Mobile SMS Protocol Message 1 - 2006-06

// source: IANA service name and port number registry

03 Check it

Which program uses port 5581, and is it reachable?

Linux

sudo ss -ltnup 'sport = :5581'      # process listening on 5581
sudo lsof -nP -i :5581

macOS

sudo lsof -nP -i :5581

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 5581 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 5581
netstat -ano | findstr :5581

From another machine

nmap -p 5581 -sV <host>
sudo nmap -sU -p 5581 <host>
nc -zv <host> 5581

Block it in the firewall

sudo ufw deny 5581/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 5581" -Direction Inbound -LocalPort 5581 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 5581 used for?

Port 5581 is assigned by IANA to tmosms1 (T-Mobile SMS Protocol Message 1).

Is port 5581 TCP or UDP?

Port 5581 is registered for TCP and UDP.

Is it safe to open port 5581?

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 5581 is open?

On Linux run "ss -ltnup 'sport = :5581'", on macOS "lsof -nP -i :5581", and on Windows "netstat -ano | findstr :5581" to see the local process. From another machine, "nmap -p 5581 <host>" shows whether it is reachable.

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