Finding the serial device COM port

Question

I have a Windows C# application . The application connects to a RFID card reader over serial port . Though i have given it COM port 3 by default . I land into situations where user's port is not available and his port being used is something different by his windows OS.

My application does give user the ability to change the COM port , but to find which COM port is being used by their operating system , user needs to go to Device Manager and check , which a novice person might not be comfortable with .

Is there a function or a way to find exactly to what port is my RFID card connected to in Windows , so that i can simply display like :

Application Port Set to : COM .... Device Connection Port on OS : COM ....

Also my target framework is 3.5

Edit 1:

Tried using SerialPort.GetPortNames() but it returns an empty string as : System.String[]..

My RFID device is listed under Device Manager ===> Ports(COM & LPT) as Silicon Labs CP210x USB to UART Bridge (COM3)

Answer 1

using System;
using System.Threading.Tasks;
namespace XYZ{
public class Program
{
    public static void Main(string[] args)  
    {
        Task<string> t = Task.Run( () =>
        { 
            return FindPort.GetPort(10);
        });
        t.Wait();

        if(t.Result == null) 
            Console.WriteLine($"Unable To Find Port");
        else
            Console.WriteLine($"[DONE] Port => {t.Result} Received");


        // Console.ReadLine();
    }
}
}

using System;
using System.IO.Ports;
public static class FindPort
{
    public static string GetPort(int retryCount)
    {
        string portString = null;
        int count = 0;
        while( (portString = FindPort.GetPortString() ) == null) {
            System.Threading.Thread.Sleep(1000);
            if(count > retryCount) break;
            count++;
        }
        return  portString;
    }
    static string GetPortString()
    {
        SerialPort currentPort = null;
        string[] portList = SerialPort.GetPortNames();

        foreach (string port in portList)
        {
            // Console.WriteLine($"Trying Port {port}");
            if (port != "COM1")
            {
                try
                {
                    currentPort = new SerialPort(port, 115200);
                    if (!currentPort.IsOpen)
                    {
                        currentPort.ReadTimeout = 2000;
                        currentPort.WriteTimeout = 2000;

                        currentPort.Open();
                        // Console.WriteLine($"Opened Port {port}");

                        currentPort.Write("connect");

                        string received = currentPort.ReadLine();

                        if(received.Contains("Hub"))
                        {
                            // Console.WriteLine($"Opened Port {port} and received {received}");

                            currentPort.Write("close");
                            currentPort.Close();

                            return port;
                        }
                    }
                }
                catch (Exception e)
                {
                    //Do nothing
                    Console.WriteLine(e.Message);

                    if(currentPort.IsOpen)
                    {
                        currentPort.Write("close");
                        currentPort.Close();
                    }
                }
            }
        }
        // Console.WriteLine($"Unable To Find Port => PortLength : {portList.Length}");
        return null;
    }
}

Answer 2

Hi @user3828453 how about the following and then you can, just use the correct port number which is returned if you still have an empty port than you have to ask the user to go into device manager and update the port via your interface.

private static string GetRFIDComPort()
{
  string portName = "";

  for ( int i = 1; i <= 20; i++ )
  {
    try
    {
      using ( SerialPort port = new SerialPort( string.Format( "COM{0}", i ) ) )
      {
        // Try to Open the port
        port.Open();

        // Ensure that you're communicating with the correct device (Some logic to test that it's your device)

        // Close the port
        port.Close();
      }

    }
    catch ( Exception ex )
    {
      Console.WriteLine( ex.Message );
    }
  }

  return portName;
}