The Industrial Raspberry Pi Forum

Posted: **12 Jan 2023, 13:13**

Hello,
I am using a Revpi Compact on which I have loaded a software that uses the port 502. Unfortunately it would appear that despite having disabled modbus communication from the web interface port 502 is not usable.
Can you tell me how to make it available?
Thank you

Posted: **13 Jan 2023, 15:57**

Hello Davide,
to check the listening ports and applications on Linux.

Code: Select all

Open a terminal application i.e. shell prompt.

Run any one of the following command on Linux to see open ports: $ sudo lsof -i -P -n | grep LISTEN. $ sudo netstat -tulpn | grep LISTEN. ...

For the latest version of Linux use the ss command. For example, ss -tulw.

Note that: Ports below 1024 are restricted - only apps with root privileges can listen on those. Of course, your application isn't privileged.

That's the general rule on Linux/Unix (and Android is Linux-based).
See this answer for a rationale behind this restriction.

Best Regards

Ulrich Kouatang Biakoup | Technical Support

The Industrial Raspberry Pi Forum

Port 502 not available

Port 502 not available

Re: Port 502 not available