how to reference entry point in an external dll (C# / unity 3D)

Question

I am using Unity 3D for an application I need to use Serial Port but in Unity, there's a missing implementation of event DataReceived and others linked functions. Therefore I think the solution is to make my own DLL that can manage Serial Port data and call it from unity as an external DLL.

I wrote the code below. the code in my class library project (just a serial port froze opening for the test)

Code:

using System;
using System.IO.Ports;

namespace serialPortManager2
{
    public class laserManager
    {
        private SerialPort laserComPort;

        public bool  open()
        {
            bool laserSerialPortDetected = false;
            // ouverture du port série pour pilotage du laser
            foreach (string portName in SerialPort.GetPortNames())
            {
                if (portName == "COM4") laserSerialPortDetected = true;
            }
            if (laserSerialPortDetected)
            {
                laserComPort = new SerialPort("COM4", 9600, Parity.None, 8, StopBits.One);
                laserComPort.Open();
                if (laserComPort.IsOpen)
                {
                    // timeout de lecture d'une mesure laser
                    laserComPort.ReadTimeout = 5000;
                    return true;
                }
                else return false;
            }
            else return false;
        }
    }
}

Code to reference DLL in Unity:

using System.Collections;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using UnityEngine;

public static class SPNativePlugIn {

// The name of the external library containing the native functions
private const string LIBRARY_NAME = "serialPortManager2";

[DllImport(LIBRARY_NAME)] public static extern bool open();

}

My problem is that I get this error: EntryPointNotFoundException: open

I guess I have to integrate the laserManager class somewhere but I do not know the syntax, I tried quite a few things but I can not find it.

Answer 1

Create a folder named "Plugins" in the "Assets" Folder then put your .dll file in the "Plugins" folder and import it in your script in this way using dllFileName;

This works for every .dll not include in the unity default library