CyberHunter
Local dataset, no network
// Other services

Port 243: Survey Measurement

Port 243 is assigned by IANA to sur-meas (Survey Measurement).

243

How sur-meas works

Other services
client:243sur-measresponse client:243sur-measresponse

The client sends a request to port 243 and the sur-meas 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 243 dangerous?

We have no specific security note for port 243. 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 243

ServicePortTransportDescriptionReferenceUpdated
sur-meas 243 TCP, UDP Survey Measurement - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 243, and is it reachable?

Linux

sudo ss -ltnup 'sport = :243'      # process listening on 243
sudo lsof -nP -i :243

macOS

sudo lsof -nP -i :243

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 243 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 243
netstat -ano | findstr :243

From another machine

nmap -p 243 -sV <host>
sudo nmap -sU -p 243 <host>
nc -zv <host> 243

Block it in the firewall

sudo ufw deny 243/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 243" -Direction Inbound -LocalPort 243 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 243 used for?

Port 243 is assigned by IANA to sur-meas (Survey Measurement).

Is port 243 TCP or UDP?

Port 243 is registered for TCP and UDP.

Is it safe to open port 243?

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 243 is open?

On Linux run "ss -ltnup 'sport = :243'", on macOS "lsof -nP -i :243", and on Windows "netstat -ano | findstr :243" to see the local process. From another machine, "nmap -p 243 <host>" shows whether it is reachable.

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