停止Stream.BeginRead() [英] Stop Stream.BeginRead()

问题描述

我需要从我的虚拟com端口读取数据并检测到消息"Dreq".一旦按下连接按钮，它将连接到我的COM8端口并开始读取新线程.我也有一个断开按钮，我想在其中关闭读数并断开与COM8端口的连接.但是，我在关闭BeginRead时遇到问题.

i need to read data from my virtual com port and detect the message "Dreq". Once i press the connect button, it connects to my COM8 port and begins reading in a new thread. I also have a disconnect button in which i wish to close the reading and disconnect from the COM8 port. However, i have problems closing the BeginRead.

public partial class Form1 : Form
{
    SerialPort sp;
    Stream stream;
    IAsyncResult recv_result;

    private void button1_Click(object sender, EventArgs e)
    {
        sp = new SerialPort("COM8", 9600);
        sp.Open();
        sp.ReadTimeout = 50000;
        sp.NewLine = "\n\r\0";
        stream = sp.BaseStream;
        recv_result = stream.BeginRead(new byte[1], 0, 0, new 
                                       AsyncCallback(ReadCallBack), stream);
    }

    private void ReadCallBack(IAsyncResult ar)
    {            
        Stream stream = (Stream)ar.AsyncState;
        string temp;

        while (stream.CanRead)
        {
            temp = sp.ReadLine();                
            // ... do something with temp
        }
    }

    private void disconnectButton_Click(object sender, EventArgs e)
    {
        stream.EndRead(recv_result);
        sp.Close();
    }
}

推荐答案

您可以尝试此程序.

using System;
using System.Windows.Forms;
using System.IO.Ports;
using System.Threading;
using System.IO;
using System.Text;

public class clsState {
    private const int BUFFER_SIZE = 1024;
    public byte[] BytesBuffer = new byte[BUFFER_SIZE];
    public SerialPort sp;
    public Stream stream;
}

public partial class Form1 : Form {

    SerialPort sp;
    Stream stream;
    IAsyncResult recv_result;

    bool endLoop = false;
    Thread _readThread;
    private ManualResetEvent _readDone = new ManualResetEvent(false);

    private void button1_Click(object sender, EventArgs e) {
        sp = new SerialPort("COM8", 9600);
        sp.Open();
        sp.ReadTimeout = 50000;
        sp.NewLine = "\n\r\0";
        stream = sp.BaseStream;

        // save serial port and stream to state object
        clsState state =  new clsState();
        state.sp = sp;
        state.stream = stream;

        // create worker thread
        endLoop = false;
        _readThread = new Thread(() => ReadThreadProc(state))
        _readThread.IsBackground = true;
        _readThread.Start();
    }

    private void ReadThreadProc(clsState state) {
        while (endLoop == false){
            // open and then close the gate as soon as after one thread passed
            _readDone.Reset();

            // starting ascynchronous read 
            recv_result = state.stream.BeginRead(state.BytesBuffer, 0, state.BytesBuffer.Length, new AsyncCallback(ReadCallBack), state.stream);

            // worker thread block in here (waiting for... _readDone.Set())
            _readDone.WaitOne();
        }
    }

    private void ReadCallBack(IAsyncResult ar) {   
        string temp;
        int bytesRead = 0;

        // read serial port and stream from IAsyncResult
        clsState state = (clsState) ar.AsyncState;

        // if port serial is open and..
        if (state.sp.IsOpen) {
            // the stream can read then..
            if(state.stream.CanRead) {
                // wait for asynchronous read to completed
                bytesRead = state.stream.EndRead(ar);
            }
        }

        if(bytesRead > 0) {
           // convert data in state.BytesBuffer from bytes array to string and save to temp variable
           temp = Encoding.ASCII.GetString(state.BytesBuffer);
            // open gate for next data
           _readDone.Set();
        }
    }

    private void disconnectButton_Click(object sender, EventArgs e) {
        // ending loop and will kill worker thread...
        endLoop = true;

        // release begin read
        _readDone.Set();      

        if (_readThread != null){
            if (_readThread.IsAlive){ // if worker thread still live
                _readThread.Join();   // wait thread off in here..
            }
        }

        // close serial port
        if (sp.IsOpen) sp.Close();

        // close stream and dispose it 
        if (stream.CanRead || stream.CanWrite) {
            stream.Close();
            stream.Dispose();
        }
    }
}

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