PC PLC communication modbus TCP IP slave

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Hi All,

I am developing .net win app to connect Mitsubishi FX5U PLC through Modbus TCP/IP Communication Protocol.

I need to make communication as PLC as Master & PC as Slave.

Can anybody have prepared such code for Connection, WriteSingleRegister and ReadHoldingRegister?

What I have tried:

I have used EasyModbus DLL and tried following code

C#

EasyModbus.ModbusClient myModbusClient = new EasyModbus.ModbusClient();
myModbusClient.IPAddress = "192.168.3.20";
myModbusClient.Port = 502;
myModbusClient.ConnectionTimeout = 2500;
tRead = new Thread(new ThreadStart(Read));
tRead.Start();
if (myModbusClient.Connected == false)
{
    try
    {
        //myModbusClient.Connect();
        myModbusClient.Connect("192.168.3.20", 502);
    }
    catch (Exception ex)
    {
        MessageBox.Show("Disconnected");
    }
}

But I am getting error "No connection could be made because the target machine actively refused it"

Posted 18-Oct-22 0:45am

Prasad G1982

Updated 18-Oct-22 2:38am

Richard Deeming

v3

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Richard Deeming · Answer 1 · 2022-10-18T02:38:00

Solution 1

The error "the target machine actively refused it" means the remote computer has a firewall which is not configured to allow your machine to talk to it on the specified port.

You need to update the firewall rules on the remote computer (192.168.3.20).

Posted 18-Oct-22 2:38am

Richard Deeming

Updated 18-Oct-22 2:39am

v2

Comments

Prasad G1982 19-Oct-22 5:01am

Actually I am trying to Connect PLC (Programmable Logic Controller) which does not contain firewall setting

It has only IP Address and PORT Settings.

And on my laptop firewall is set off.

Richard Deeming 19-Oct-22 6:09am

Then either the port is wrong, or the IP address you're connecting to isn't the PLC. "Actively refused" means something at the remote end received your connection request and rejected it. That's a different error from what you'd get if there was nothing listening on that port, or nothing using the specified IP address.