How to find which serial port is currently used?

Question

I ve connected my mobile phone to my PC and used this,

string[] lPorts = System.IO.Ports.SerialPort.GetPortNames();

and the result was an array of port names

"COM4"
"COM3"
"COM1"
"COM7"
"COM6"

Now,How to find which serial port is currently used/to which port my mobile phone is connected in c#?

Answer 1

Obviously you will need to know the serial protocol being used to communicate. Just send a known command to each port and check back for the expected response. Ports with no device on them will timeout/throw an IOException.

Or you if you don't want to do this through code you can try the same using HyperTerminal or another serial terminal program.

Try something like following: (Please note I am writing this from memory and don't guarantee this will compile/that I have the method names 100% right, but it gives the general idea).

foreach(string portname in SerialPort.GetPortNames())
{
    // Use your connection settings - own baud rate etc
    SerialPort sp = new SerialPort(portname,4800, Parity.Odd, 8, StopBits.One); 
    try
    {
         sp.Open();
         sp.Write("Your known command to phone");
         Thread.Sleep(500);
         string received = sp.ReadLine();

         if(received == "expected response")
         {
              Console.WriteLine("Phone connected to: " + portname);
              break;
         }
    }
    catch(Exception)
    {
         Console.WriteLine("Phone NOT connected to: " + portname);
    }
    finally
    {
         sp.Close();
    }
}