Monitor UDP Port

Alerts and Toolboxes
1

Anyone know of a good way to monitor a UDP port and get alerted when the UDP port is not responding?

2

Not sure if you mean locally (checking if port is open on local machine), or remotely (checking if a port is open on a different machine).

Here’s some links to look at though…

  1. https://docs.microsoft.com/en-US/troubleshoot/windows-server/networking/portqry-command-line-port-scanner-v2
  2. https://www.nirsoft.net/utils/cports.html

Feel free to post more info on what you are trying to do.

3

There is no good way that I have found since it’s a connectionless protocol. Depends on what you want to accomplish. I have used Microsoft portqry in the past - the link @realmx2 posted.
Or if you’re using Linux you can send a ping. https://networkengineering.stackexchange.com/questions/26541/how-to-verify-that-a-udp-port-is-open
You could also use ncat or nmap to see if its open or listening. https://serverfault.com/questions/416205/testing-udp-port-connectivity

For me though portqry allowed me to script it in windows,
c:\portqry.exe -n REMOTEIPHERE -e 4435 -p udp

4

It is an HVAC system that I am looking to monitor that receives communication on UDP port 47808. I have tried to write a script/toolbox using both portqry, ncat and nmap and I can’t get a different status result on it being up or down. Thankfully an ICMP ping script I have works but I was looking for something a little more reliable.

5

Oof, ya some of those HVAC systems are ugly. And with udp that doesnt help. Sorry.
You would probably need to know a command that would send a response and use netcat to script sending that command to the port since udp is connectionless and your device is ignoring all other communication.