26

我已经构建了一个从串行端口读取和写入数据的 C# 应用程序。连接到串行端口的设备是一个 FTDI USB 到串行转换器，它通过 XBee 无线模块与硬件通信。硬件测试电池模块的容量和稳态电压等。这些测试需要几天时间才能完成。

串行端口似乎不时停止响应并抛出 System.IO.IOException: A device attach to the system is not running 错误。

这是堆栈跟踪：

at system.IO.Ports.InternalResources.WinIOError
at system.IO.Ports.SerialStream.EndWrite
at system.IO.Ports.SerialStream.Write
at system.IO.Ports.SerialPort.Write
at BatteryCharger.CommunicationClass.ApiTransmission

引发此错误后，将引发System.UnauthorizedAccessException: Access to the port is denied错误，并且每次软件尝试写入端口时都会发生此错误，并且在我停止调试并重新启动软件之前，它永远不会恢复，仅在几天后发生同样的事情。

如何防止此错误发生，或者有没有办法在错误的 catch 语句中成功地从这些错误中恢复？

我在后台工作线程中连续读取串行端口并从不同的线程写入。

我也已经尝试过这个论坛上建议的所有遗留错误处理点点滴滴，但它们似乎都没有任何区别。该错误发生在 windows XP Pro SP3 32bit 和 Windows7 Pro 32bit 上。

这是 CommunicationClass.cs - 串行传输代码。

    public static bool ApiTransmission(TXpacket transmission)
    {
        //clear all previous data that may have been in the buffer before doing a transmission
        Variables.dataParserPacket_buff.Clear();
        //TXpacket xbeetransmision = new TXpacket();
        byte[] packet = transmission.GeneratePacket();

        try
        {
            if (_serialPort.IsOpen)
            {
#if Console
                Log.write("TX-Packet: " + StringHandler.listToString(packet.ToList<byte>()));
#endif
                _serialPort.Write(packet, 0, packet.Length);
                Thread.Sleep(100);
            }
            else
            {
#if Console
                Log.write("serial port is closed");
#endif
                return false;
            }
        }
        catch (UnauthorizedAccessException ex)
        {
            MessageBox.Show(ex.ToString());
            Log.write("UnauthorizedAccessException");
        }
        catch (IOException ex)
        {
            MessageBox.Show(ex.ToString());
            Log.write("IOexception");
            //_serialPort.Close();
            //Thread.Sleep(100);
            //_serialPort.Open();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.ToString());
#if Console
            Log.write(ex.ToString());
#endif
        }
        return true;

    }

这就是我初始化串口的方式

    public CommunicationClass(string portName, int baudRate, Parity parity, int dataBits, StopBits stopBits)
    {
        _analysePacketBGW.DoWork += new DoWorkEventHandler(_analysePacketBGW_DoWork);
        _analysePacketBGW.WorkerReportsProgress = true;
        _analysePacketBGW.WorkerSupportsCancellation = true;

        _readBGW.DoWork += new DoWorkEventHandler(_readThread_DoWork);
        _readBGW.WorkerSupportsCancellation = true;
        _readBGW.WorkerReportsProgress = true;

        _parserStarterBGW.DoWork += new DoWorkEventHandler(_parserStarterThread_DoWork);
        _parserStarterBGW.WorkerSupportsCancellation = true;
        _parserStarterBGW.WorkerReportsProgress = true;
        if (_readBGW != null)
        {
            _readBGW.CancelAsync();
        }

        _serialPort = new SerialPort(portName, baudRate, parity, dataBits, stopBits);

        //SerialPortFixer.Execute(portName);
        //Thread.Sleep(1000);
        //using (_serialPort = new SerialPort(portName, baudRate, parity, dataBits, stopBits))
        //{
        //    //_serialPort.Open();
        //}

        _serialPort.ErrorReceived += new SerialErrorReceivedEventHandler(_serialPort_ErrorReceived);

        _dataqueuepp = new ManualResetEvent(false);

        _serialPort.Open();
        _readBGW.RunWorkerAsync();
        _parserStarterBGW.RunWorkerAsync();
        CommunicationClass.PacketReceived += new DataPacketReceived(CommunicationClass_PacketReceived);
    }

以及处理串口读取的后台工作者

    void _readThread_DoWork(object sender, DoWorkEventArgs e)
    {
#if Console
        Log.write("Read()");
#endif
        while (!_readBGW.CancellationPending)
        {
            try
            {
                int message = _serialPort.ReadByte();
                try
                {
                    Variables.dataQueue.Enqueue(message);
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message + "     " + message.ToString());
                }
                _dataqueuepp.Set();
                //Console.Write(String.Format("{0:X2}", message) + " ");
            }
            catch (TimeoutException) { Log.write("read timeout"); }
            catch (IOException) { Log.write("read IOException"); }
            catch (ThreadAbortException) { Log.write("read thread aborted"); }
            catch (Exception ex) { MessageBox.Show(ex.ToString()); }
            finally { }
        }
    }

我现在将重写代码以从同一个线程读取和写入串行端口，看看这是否有任何区别。

编辑

根据 Jim 的评论，我在 IOException Catch 语句中添加了以下内容：

        catch (IOException ex)
        {
            MessageBox.Show(ex.ToString());
            Log.write("IOexception");
            _readBGW.CancelAsync();
            Thread.Sleep(100);
            _serialPort.Close();
            Thread.Sleep(100);
            _serialPort.Open();
            Thread.Sleep(100);
            _readBGW.RunWorkerAsync();
            _serialPort.Write(packet, 0, packet.Length);
        }

希望通过停止后台工作程序的 _serialPort.Read、关闭端口、重新打开端口、再次运行后台工作程序并再次尝试编写相同的命令足以成功地从该错误中恢复。MessageBox 仍然阻止代码，以便我可以看到错误何时发生并可以监控它是如何恢复的。

我不喜欢像这样修补软件，但如果它有效，那么它就有效。

编辑 2

添加上面的代码后，我的软件再次崩溃，但现在当我调用 _serialPort.Close(); 时它会抛出“UnauthorizedAccessException - 拒绝访问端口”；

System.UnauthorizedAccessException was unhandled
Message=Access to the port is denied.
Source=System
StackTrace:
at System.IO.Ports.InternalResources.WinIOError(Int32 errorCode, String str)
at System.IO.Ports.InternalResources.WinIOError()
at System.IO.Ports.SerialStream.Dispose(Boolean disposing)
at System.IO.Stream.Close()
at System.IO.Ports.SerialPort.Dispose(Boolean disposing)
at System.IO.Ports.SerialPort.Close()
at BatteryCharger.CommunicationClass.ApiTransmission(TXpacket transmission) in E:\Mijn Documenten\Research\Copy of BatteryCharger_V12\BatteryCharger\CommunicationClass.cs:line 436
at BatteryCharger.CommunicationClass.tx1(TXpacket packet, String callingMethod) in E:\Mijn Documenten\Research\Copy of BatteryCharger_V12\BatteryCharger\CommunicationClass.cs:line 356
at BatteryCharger.XBee.setPin(String pinID, Byte status, XBee slave) in E:\Mijn Documenten\Research\Copy of BatteryCharger_V12\BatteryCharger\XBee.cs:line 215
at BatteryCharger.XBee.setPins(Int32 pins, XBee slave) in E:\Mijn Documenten\Research\Copy of BatteryCharger_V12\BatteryCharger\XBee.cs:line 177
at BatteryCharger.BatteryCharger.requestVoltage(Int32 block) in E:\Mijn Documenten\Research\Copy of BatteryCharger_V12\BatteryCharger\BatteryCharger.cs:line 595
at BatteryCharger.BatteryCharger.requestVoltages() in E:\Mijn Documenten\Research\Copy of BatteryCharger_V12\BatteryCharger\BatteryCharger.cs:line 612
at BatteryCharger.Form1.RunCommandOn(List`1 battList, Int32 command, Double lowerLimit, Double upperLimit) in E:\Mijn Documenten\Research\Copy of BatteryCharger_V12\BatteryCharger\Form1.cs:line 522
at BatteryCharger.Form1.chargeBlock(Int32 blockNr, Double lowerLimit, Double upperLimit) in E:\Mijn Documenten\Research\Copy of BatteryCharger_V12\BatteryCharger\Form1.cs:line 689
at BatteryCharger.Form1.<btnCheckCapacities_Click>b__13() in E:\Mijn Documenten\Research\Copy of BatteryCharger_V12\BatteryCharger\Form1.cs:line 619
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
InnerException:

这里发生了什么？

4

3 回答 3

3

根据我的经验，10 次中有 9 次发生这种情况时，另一个线程（终止与否）没有对硬件端口的独占访问权。

尝试使用SyncLock为端口操作编写一个包装器，最重要的是它的打开/关闭。https://msdn.microsoft.com/en-us/library/3a86s51t.aspx

同样，除非有足够的异常处理，否则我通常会认为尝试/捕获控制硬件是一种不好的做法。

原因（可能适用于此）是在抛出异常的情况下，硬件将锁定，更糟糕的是，异常将掩盖错误的真正原因。

在上面的代码中，我看到了样式中的消息输出

DebugPrint(ex.Message);

这样做会更好

DebugPrint(ex.tostring());

因为这也会在异常中导出堆栈跟踪。

我要做的是实现一个异常记录器，它将这些异常写入正在运行的计算机中某处的（时间戳）文本文件中。跟踪记录的异常数据（以及所有相关信息）可以更好地理解为什么会发生这种情况。

于 2015-10-27T01:39:06.840 回答
2

我密集使用 SerialPort 类通过 USB 适配器与 PLC 连续通信数月，没有任何中断。所以我不能同意谁说 SerialPort .NET 类不起作用。尝试将类的创建插入线程，这里是 BackgroundWorker 的代码示例。

    void ThreadEngine_DoWork(object sender, DoWorkEventArgs e)
    {
        // Do not access the form's BackgroundWorker reference directly.
        // Instead, use the reference provided by the sender parameter.
        BackgroundWorker objBackgroundWorker = sender as BackgroundWorker;

        try
        {
            mSerialPort = new SerialPort(GetPortName(mPortName), DefaultBaudRate, Parity.Even, 7, StopBits.Two);
            mSerialPort.Open();
            objBackgroundWorker.ReportProgress(0);

            while (objBackgroundWorker.CancellationPending == false)
            {
                if (IOScanner(objBackgroundWorker, false) == true)
                {
                    ScannerStationData();
                    IsReady = true;
                    IsError = false;
                }
                else
                {
                    IsReady = false;
                    IsError = true;
                }
                Thread.Sleep(1);
            }

            // Performs last scan before thread closing
            if (objBackgroundWorker.CancellationPending == true)
            {
                IOScanner(objBackgroundWorker, true);
            }

            mSerialPort.Close();
            mSerialPort = null;
            e.Result = null;
        }
        catch (Exception objErr)
        {
            string sMessage = string.Format("PlcService.ThreadEngine_DoWork Err={0}", objErr.Message);
            mLogSysService.AddItem(sMessage);
            IsError = true;
        }
    }

方法 IOScanner 调用其他方法进行通信，如下面的。

    protected bool WriteDMWord(int iAddress, int[] aryValues)
    {
        bool bRetValue = true;
        try
        {
            mSerialPort.NewLine = "\r";
            mSerialPort.ReadTimeout = DefaultTimeout;
            string sTxData = HostLinkProtocol.BuildWriteDMWord(iAddress, aryValues);
            mSerialPort.WriteLine(sTxData);

            string sRxData = string.Empty;
            sRxData = mSerialPort.ReadLine();
            if (HostLinkProtocol.ParseWriteDMWord(sRxData) == true)
            {
                bRetValue = true;
            }
        }
        catch (Exception objErr)
        {
            Console.WriteLine("WriteDMWord [{0}]", objErr.Message);
            bRetValue = false;
        }
        return bRetValue;
    }
于 2015-10-15T06:11:40.773 回答
0

我使用 FTDI USB，并在 Serial .net 类上与它通信，有时在 WindowsXp 上我有这种异常，我用 devcon.exe 解决它，我执行禁用和启用，但没有出现错误。

于 2019-12-14T15:04:49.920 回答