我已经构建了一个C＃应用程序，它可以从串口读取和写入数据。连接到串行端口的设备是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。这些测试需要数天才能完成。
串口似乎停止响应并抛出System.IO.IOException：连接到系统的设备无法正常运行错误。
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
抛出此错误后会抛出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，并且它永远不会恢复，直到我停止调试并重新启动软件只是为了发生同样的事情几天后。
如何防止此错误发生或有没有办法从错误的catch语句中成功恢复这些错误？
我正在后台工作线程中连续读取串口并从另一个线程写入。
我也已经尝试过在本论坛上提出的所有遗留错误处理部分，但它们似乎都没有任何区别。 Windows XP Pro SP3 32位和Windows7 Pro 32位上出现错误。
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;
}
这是我初始化串口的方法
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);
}
处理读取串口的后台工作程序
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，以查看是否有任何区别。
修改
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者的_serialPort.Read，关闭端口，重新打开端口，再次运行后台工作程序并尝试再次写入相同的命令，就足以成功从此错误中恢复。 MessageBox仍然阻止代码，以便我可以看到错误发生的时间，并可以监视它是如何恢复的。
我不喜欢修补这样的软件，但如果它有效，那么它可以工作。
编辑2
添加上面的代码之后，我的软件再次崩溃，但是现在当我调用_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？
答案 0 :(得分：2)
根据我的经验，当有另一个线程（终止或未终止）没有对硬件端口的独占访问时，会发生9次中的9次。
尝试使用 SyncLock 为端口操作编写包装器，最重要的是打开/关闭它。 https://msdn.microsoft.com/en-us/library/3a86s51t.aspx
在类似的说明中，我通常认为尝试/捕获控制硬件是一种不好的做法，除非有足够的异常处理。
原因（可以在这里应用）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
的消息输出DebugPrint(ex.Message);
像
这样做会更好DebugPrint(ex.tostring());
因为这也将导出异常中的堆栈跟踪。
我要做的是实现一个异常记录器，将这些异常写入正在运行的计算机中某个（带时间戳的）文本文件。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。
答案 1 :(得分：1)
我使用密集的SerialPort类通过USB适配器与PLC连续通信数月而不会中断。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到线程中，这是使用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，如下一个。
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;
}
答案 2 :(得分：0)
我使用FTDI USB，并且在Serial .net类上与它进行通信，有时在WindowsXp上，我遇到这种异常，我使用devcon.exe解决了该问题，执行了禁用和启用操作，但未出现该错误。