Modbus TCP/IP localhost

Hi,

I would like to set up a modbus communication using TCP/IP.

In order to test it, I wanted to set the communication between two Matlab sessions on the same computer and set up the communication using local IP address.

To do so, I tested the following:

m = modbus('tcpip', 'localhost');

or

m = modbus('tcpip', '127.0.0.1');

but in both case I get the following error:

Error using modbus (line 96)
Requested transport resource is either in use or does not exist. Unsuccessful open: Connection refused (Connection
refused)

Is it related to a configuration that I have not done on my computer or is it impossible to set up such a communication?

Thanks for your help.

[Walter Roberson]

Sometimes it is firewall issues on Windows.

[Ming Yue]

If you want to transfer data between two MATLAB sessions, you can consider using the "tcpip" connection. Here's an example: https://blogs.mathworks.com/loren/2011/05/27/transferring-data-between-two-computers-using-matlab/.

The example is for sending info from one MATLAB session to another (one direction), so you can setup a server and a client on each MATLAB session with different port number to communicate in both directions.

[M]

This was indeed a firewall issue. Thanks for your help.

Answer 1

[M]

This was a firewall issue. Ubuntu has a built-in firewall that one can deactivate using this solution:

<https://askubuntu.com/questions/250775/how-do-i-turn-off-the-firewall-in-ubuntu-12-04>