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// Other services

Port 257: Secure Electronic Transaction

Port 257 is assigned by IANA to set (Secure Electronic Transaction).

257

How set works

Other services
client:257setresponse client:257setresponse

The client sends a request to port 257 and the set 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 257 dangerous?

We have no specific security note for port 257. 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 257

ServicePortTransportDescriptionReferenceUpdated
set 257 TCP, UDP Secure Electronic Transaction - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 257, and is it reachable?

Linux

sudo ss -ltnup 'sport = :257'      # process listening on 257
sudo lsof -nP -i :257

macOS

sudo lsof -nP -i :257

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 257 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 257
netstat -ano | findstr :257

From another machine

nmap -p 257 -sV <host>
sudo nmap -sU -p 257 <host>
nc -zv <host> 257

Block it in the firewall

sudo ufw deny 257/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 257" -Direction Inbound -LocalPort 257 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 257 used for?

Port 257 is assigned by IANA to set (Secure Electronic Transaction).

Is port 257 TCP or UDP?

Port 257 is registered for TCP and UDP.

Is it safe to open port 257?

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 257 is open?

On Linux run "ss -ltnup 'sport = :257'", on macOS "lsof -nP -i :257", and on Windows "netstat -ano | findstr :257" to see the local process. From another machine, "nmap -p 257 <host>" shows whether it is reachable.

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