Question

I have a thread in a function which start the live monitoring, it basically, opens the serial port and continously reading data from serial port. However, If I need to terminate this thread, how should I do it? Because If I don’t terminate the running thread which opened the specific serial port and reading data. When I close it and call the function again. The same serial port cannot opened. I suspect that the serial port is not closed properly and is still running in a seperate thread. So I think i have to terminate that thread in order to open the same serial port again next time. Does anyone have any idea of how to achieve this?

I have seen some forum said that Thread.Abort() is dangerous to use. It should only be used in last resort.

Thanks for any helps.

Charles

Answer 1

Generally, you design the method that is run in the background thread to listen for cancellation requests. This can be as simple as a boolean value:

//this simply provides a synchronized reference wrapper for the Boolean,
//and prevents trying to "un-cancel"
public class ThreadStatus
{
   private bool cancelled;

   private object syncObj = new Object();

   public void Cancel() {lock(syncObj){cancelled = true;}}

   public bool IsCancelPending{get{lock(syncObj){return cancelled;}}}
}

public void RunListener(object status)
{
   var threadStatus = (ThreadStatus)status;

   var listener = new SerialPort("COM1");

   listener.Open();

   //this will loop until we cancel it, the port closes, 
   //or DoSomethingWithData indicates we should get out
   while(!status.IsCancelPending 
         && listener.IsOpen 
         && DoSomethingWithData(listener.ReadExisting())
      Thread.Yield(); //avoid burning the CPU when there isn't anything for this thread

   listener.Dispose();
}

...

Thread backgroundThread = new Thread(RunListener);
ThreadStatus status = new ThreadStatus();
backgroundThread.Start(status);

...

//when you need to get out...
//signal the thread to stop looping
status.Cancel();
//and block this thread until the background thread ends normally.
backgroundThread.Join()