Serial port communication throwing TimeoutException

问题

Following up with Serial Port Communication solution I implemented the below design. My code uses com8 to communicate with a Serial Port Utility Application that is listening on com9 within the same machine, then sending back (manually I type a message and press a button)

In my main I do this:

MyClass MyObj = new MyClass();
var message = MyObj.SendThenRecieveDataViaSerialPort("Test");

And then in my class I have this:

private static SerialPort MainSerialPort { get; set; } = new SerialPort();
private static string _ReceivedMessage;
private Thread readThread = new Thread(() => ReadSerialPort(ref _ReceivedMessage));

public string SendThenRecieveDataViaSerialPort(string _Message)
{
    MainSerialPort = new SerialPort("com8", 9600);
    MainSerialPort.ReadTimeout = 5000;
    MainSerialPort.WriteTimeout = 5000;
    MainSerialPort.Open();
    readThread.Start(); // 1

    try
    { // 2
        MainSerialPort.WriteLine(_Message); // 3
        readThread.Join(); // 6 - Console pops and waits
    }
    catch (TimeoutException ex)
    {
        Console.WriteLine("Exception in SendThenreceive");
    }

    return _ReceivedMessage;
}

private static void ReadSerialPort(ref string _message)
{
    try
    { // 4
        _message= MainSerialPort.ReadLine(); // 5 
    }
    catch (TimeoutException ex)
    {
        // 7 - when time outs
    }
}

However, it is throwing an error at step 7 saying:

{"The operation has timed out."}

InnerException: null

Could you tell me where I am going wrong? Please and thanks.

回答1:

ReadLine waits until it sees the SerialPort.NewLine string. If this doesn't arrive within SerialPort.ReadTimeout the TimeoutException is thrown. So don't miss to send the NewLine!

Here is an alternative version without NewLine.

byte[] data = new byte[1024];
int bytesRead = MainSerialPort.Read(data, 0, data.Length);
_message = Encoding.ASCII.GetString(data, 0, bytesRead);

来源：https://stackoverflow.com/questions/39349409/serial-port-communication-throwing-timeoutexception

标签

multithreading

serial-port