吵吵   2015-12-11  阅读:1,945

在我写SerialServer即串口转网口程序的时候,串口通讯的类是从网上Download的一个CSerailPort类,这是个老外在1997年写的一个类,当然在2012年有人修改过了,处理过一些bug。但是比较困扰我的是,它接收到数据是一个char(一个字节)读取的,这导致我写的日志里面都是这个样子的:

a
b
c
d
e
….

如果我要拼凑起来,就得一个个拷贝,这在串口的调试过程中,非常麻烦。

没有办法,就只能自己再仔细的读了一下这个类的代码,然后修正这些代码。

该类是一个多线程的异步通讯类,用到的是事件对象(envet)来进行同步,我们可以看下核心的代码:

UINT CSerialPort::CommThread(LPVOID pParam)
{
	// Cast the void pointer passed to the thread back to
	// a pointer of CSerialPort class
	CSerialPort *port = (CSerialPort*)pParam;
	
	// Set the status variable in the dialog class to
	// TRUE to indicate the thread is running.
	port->m_bThreadAlive = TRUE;	
		
	// Misc. variables
	DWORD BytesTransfered = 0; 
	DWORD Event = 0;
	DWORD CommEvent = 0;
	DWORD dwError = 0;
	COMSTAT comstat;

	memset(&comstat, 0, sizeof(COMSTAT)); //initial comstate 2015-11-21 chaochao
	BOOL  bResult = TRUE;
		
	// Clear comm buffers at startup
	if (port->m_hComm)		// check if the port is opened
		PurgeComm(port->m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);

	// begin forever loop.  This loop will run as long as the thread is alive.
	for (;;) 
	{ 

		// Make a call to WaitCommEvent().  This call will return immediatly
		// because our port was created as an async port (FILE_FLAG_OVERLAPPED
		// and an m_OverlappedStructerlapped structure specified).  This call will cause the 
		// m_OverlappedStructerlapped element m_OverlappedStruct.hEvent, which is part of the m_hEventArray to 
		// be placed in a non-signeled state if there are no bytes available to be read,
		// or to a signeled state if there are bytes available.  If this event handle 
		// is set to the non-signeled state, it will be set to signeled when a 
		// character arrives at the port.

		// we do this for each port!

		bResult = WaitCommEvent(port->m_hComm, &Event, &port->m_ov);

		if (!bResult)  
		{ 
			// If WaitCommEvent() returns FALSE, process the last error to determin
			// the reason..
			switch (dwError = GetLastError()) 
			{ 
			case ERROR_IO_PENDING: 	
				{ 
					// This is a normal return value if there are no bytes
					// to read at the port.
					// Do nothing and continue
					break;
				}
			case 87:
				{
					// Under Windows NT, this value is returned for some reason.
					// I have not investigated why, but it is also a valid reply
					// Also do nothing and continue.
					break;
				}
			default:
				{
					// All other error codes indicate a serious error has
					// occured.  Process this error.
					port->ProcessErrorMessage("WaitCommEvent()");
					break;
				}
			}
		}
		else
		{
			// If WaitCommEvent() returns TRUE, check to be sure there are
			// actually bytes in the buffer to read.  
			//
			// If you are reading more than one byte at a time from the buffer 
			// (which this program does not do) you will have the situation occur 
			// where the first byte to arrive will cause the WaitForMultipleObjects() 
			// function to stop waiting.  The WaitForMultipleObjects() function 
			// resets the event handle in m_OverlappedStruct.hEvent to the non-signelead state
			// as it returns.  
			//
			// If in the time between the reset of this event and the call to 
			// ReadFile() more bytes arrive, the m_OverlappedStruct.hEvent handle will be set again
			// to the signeled state. When the call to ReadFile() occurs, it will 
			// read all of the bytes from the buffer, and the program will
			// loop back around to WaitCommEvent().
			// 
			// At this point you will be in the situation where m_OverlappedStruct.hEvent is set,
			// but there are no bytes available to read.  If you proceed and call
			// ReadFile(), it will return immediatly due to the async port setup, but
			// GetOverlappedResults() will not return until the next character arrives.
			//
			// It is not desirable for the GetOverlappedResults() function to be in 
			// this state.  The thread shutdown event (event 0) and the WriteFile()
			// event (Event2) will not work if the thread is blocked by GetOverlappedResults().
			//
			// The solution to this is to check the buffer with a call to ClearCommError().
			// This call will reset the event handle, and if there are no bytes to read
			// we can loop back through WaitCommEvent() again, then proceed.
			// If there are really bytes to read, do nothing and proceed.
		
			bResult = ClearCommError(port->m_hComm, &dwError, &comstat);

			if (comstat.cbInQue == 0)
				continue;
			//没有输入
		}	// end if bResult

		// Main wait function.  This function will normally block the thread
		// until one of nine events occur that require action.
		Event = WaitForMultipleObjects(3, port->m_hEventArray, FALSE, INFINITE);
		
		switch (Event)
		{
		case 0:
			{
				// Shutdown event.  This is event zero so it will be
				// the higest priority and be serviced first.

			 	port->m_bThreadAlive = FALSE;
				
				// Kill this thread.  break is not needed, but makes me feel better.
				AfxEndThread(100);
				break;
			}
		case 1:	// read event
			{
				GetCommMask(port->m_hComm, &CommEvent);
				if (CommEvent & EV_RXCHAR) //接收到字符,并置于输入缓冲区中 
					//ReceiveChar(port, comstat);
					//AfxMessageBox("Receive char");
					ReceiveString(port, comstat);
				
				if (CommEvent & EV_CTS) //CTS信号状态发生变化
					::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_CTS_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
				if (CommEvent & EV_RXFLAG) //接收到事件字符,并置于输入缓冲区中 
					::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_RXFLAG_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
				if (CommEvent & EV_BREAK)  //输入中发生中断
					::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_BREAK_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
				if (CommEvent & EV_ERR) //发生线路状态错误,线路状态错误包括CE_FRAME,CE_OVERRUN和CE_RXPARITY 
					::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_ERR_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
				if (CommEvent & EV_RING) //检测到振铃指示
					::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_RING_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
					
				break;
			}  
		case 2: // write event
			{
				// Write character event from port
				WriteChar(port);
				break;
			}

		} // end switch

	} // close forever loop

	return 0;
}

CommThread是它的主线程,该线程会不断的循环,与我们一般的做法用Thread.Sleep来等待不同,它使用的是等待事件信号来激活线程继续动作的:
1、WaitCommEvent函数可以等待Comm口的事件,但是前提是在CreateFile即打开串口的时候,参数要写入FILE_FLAG_OVERLAPPED,即使用异步IO的模式。

使用异步模式之后,WaitCommEvent就可以马上返回了,不用去等待了,但是第三个参数是要传入一个LPOVERLAPPED的结构体的,这个结构体有些啥东西呢?

typedef struct _OVERLAPPED {
ULONG_PTR Internal;
ULONG_PTR InternalHigh;
union {
struct {
DWORD Offset;
DWORD OffsetHigh;
} DUMMYSTRUCTNAME;
PVOID Pointer;
} DUMMYUNIONNAME;

HANDLE hEvent;
} OVERLAPPED, *LPOVERLAPPED;

这个结构我们就不再仔细追究了,Internal实际对应的是IO的status,即返回的状态,当=0的时候,就是readfile返回成功,等于其它值则是一些其它对应的错误了,最重要的还有一个hEvent,来实现事件的信号。

因此,第一个函数WaitCommEvent的作用就是让线程陷入等待,直到有一些Comm的事件发生,如收到数据了,那么就顺便ClearCommError,如果有其它错误,就处理错误。但是等到Comm有数据的时候,这里暂时不去读取它了,因为后面还有一个主要的等待函数会处理这个问题:

2、WaitForMultipleObjects才是最主要的等待函数,我们看port->m_hEventArray,它有三个Event分别对应:
m_hEventArray[0] = m_hShutdownEvent; // highest priority
m_hEventArray[1] = m_ov.hEvent;
m_hEventArray[2] = m_hWriteEvent;
0是线程退出的信号,1是前面说的LPOVERLAPPED的hEvent,这里我们就知道了这个结构有什么用了,当串口有数据到达的时候,这个hEvent就变成了有信号的状态。3是写入的Event,这个一般是我们手动的reset它,以告诉线程我们要写入数据了。

好了,当三个当中的任何一个Event有信号了,函数就返回了,而且会识别出是哪个Event有信号了,继而执行后续相关的操作。

那么这个类是如何实现异步IO的,我们就非常的清楚了,接下来要解决只接受一个字符的问题,我们看它接收字符的函数:

bResult = ReadFile(port->m_hComm, // Handle to COMM port
&RXBuff, // RX Buffer Pointer
1, // Read one byte
&BytesRead, // Stores number of bytes read
&port->m_ov); // pointer to the m_ov structure

啊哈,原来是这里在捣鬼,因为它把读取的长度设置为了1,那么自然每次都只会读取一个字节罗。

既然知道问题,那么好办,new 一个char[1024]的数组来接收不就好了:

char * buff=new char[1024];
bResult = ReadFile(port->m_hComm,buff,1024,&BytesRead,&port->m_ov);

由于传入的是&port->m_ov,即异步IO,这个函数会立马返回,但是返回的bResult会是false。再看dwError = GetLastError(),你会发现得到的错误是ERROR_IO_PENDING,就是说我告诉你我读取失败是因为我还在读取呢。私以为这其实算不上是个错误,因为人家只是还在工作而已。那么如果返回的是这个错误怎么办呢?不用着急,我们有GetOverlappedResult这个函数,这个函数是干嘛用的呢,获取异步操作的状态啊,这个函数第四个参数是bWait,如果我们设置为true的话,就可以等到异步操作完成啦,于是乎我们可以用这个函数来等待读取完成,因此代码是这样的:

if (!bRead)
{
bRead = TRUE;
bResult = GetOverlappedResult(port->m_hComm, // Handle to COMM port
&port->m_ov, // Overlapped structure
&BytesRead, // Stores number of bytes read
TRUE); // Wait flag

// deal with the error code
if (!bResult)
{
port->ProcessErrorMessage(“GetOverlappedResults() in ReadFile()”);
}
} // close if (!bRead)

再一跑程序,卡在GetOverlappedResult了,为什么?即便是将bWait设置成了false,依然返回ERROR_IO_PENDING的错误,想了半天,突然明白,你看到buff[1024]这个数组么?原来它一直在读取,只是因为没有满1024!

这个就为难我了,我是把buff设置的大了,那要等数据满了才能返回是不可能的,我设置小了,又要读取多次才能取完数据,那不是又成了我一个char这么去数据了,咋办呢?

再去翻翻教程原来COMSTAT.cbInQue代表的就是收到的字节数,哈哈,这就好办了。

我就可以动态的确定buff的大小了!

char* readBuff=new char[comstat.cbInQue];

bResult = ReadFile(port->m_hComm, readBuff, comstat.cbInQue,&BytesRead,&port->m_ov);

惊奇的发现原来bResult直接就返回true了!

好了大工告成,把CSerialPort放到后面吧,自行取用了。

CSerialPort.h

/*
**	FILENAME			CSerialPort.h
**
**	PURPOSE				This class can read, write and watch one serial port.
**						It sends messages to its owner when something happends on the port
**						The class creates a thread for reading and writing so the main
**						program is not blocked.
**
**	CREATION DATE		15-09-1997
**	LAST MODIFICATION	12-11-1997
**
**	AUTHOR				Remon Spekreijse
**
**
************************************************************************************
**  author: mrlong date:2007-12-25
**
**  改进
**    1) 增加ClosePort
**    2) 增加 writetoProt() 两个方法
**    3) 增加 SendData 与 RecvData 方法
**************************************************************************************
***************************************************************************************
**  author:liquanhai date:2011-11-04
**  改进
**    1)增加 ClosePort中交出控制权,防止死锁问题
**    2) 增加 ReceiveChar中防止线程死锁
?*/

#ifndef __SERIALPORT_H__
#define __SERIALPORT_H__

#define WM_COMM_BREAK_DETECTED		WM_USER+1	// A break was detected on input.
#define WM_COMM_CTS_DETECTED		WM_USER+2	// The CTS (clear-to-send) signal changed state. 
#define WM_COMM_DSR_DETECTED		WM_USER+3	// The DSR (data-set-ready) signal changed state. 
#define WM_COMM_ERR_DETECTED		WM_USER+4	// A line-status error occurred. Line-status errors are CE_FRAME, CE_OVERRUN, and CE_RXPARITY. 
#define WM_COMM_RING_DETECTED		WM_USER+5	// A ring indicator was detected. 
#define WM_COMM_RLSD_DETECTED		WM_USER+6	// The RLSD (receive-line-signal-detect) signal changed state. 
#define WM_COMM_RXCHAR				WM_USER+7	// A character was received and placed in the input buffer. 
#define WM_COMM_RXFLAG_DETECTED		WM_USER+8	// The event character was received and placed in the input buffer.  
#define WM_COMM_TXEMPTY_DETECTED	WM_USER+9	// The last character in the output buffer was sent. 
#define WM_COMM_RECEIVE_STRING	    WM_USER+10 //Receive string

class CSerialPort
{														 
public:
	// contruction and destruction
	CSerialPort();
	virtual		~CSerialPort();

	// port initialisation											
	BOOL		InitPort(CWnd* pPortOwner, UINT portnr = 1, UINT baud = 19200, 
				char parity = 'N', UINT databits = 8, UINT stopsbits = 0, 
				DWORD dwCommEvents = EV_RXCHAR | EV_CTS, UINT nBufferSize = 512,
			
				DWORD ReadIntervalTimeout = 1000,
				DWORD ReadTotalTimeoutMultiplier = 1000,
				DWORD ReadTotalTimeoutConstant = 1000,
				DWORD WriteTotalTimeoutMultiplier = 1000,
				DWORD WriteTotalTimeoutConstant = 1000);

	// start/stop comm watching
	BOOL		StartMonitoring();
	BOOL		RestartMonitoring();
	BOOL		StopMonitoring();

	DWORD		GetWriteBufferSize();
	DWORD		GetCommEvents();
	DCB			GetDCB();

	void		WriteToPort(char* string);
	void        WriteToPort(char* string,int n); // add by mrlong 2007-12-25
	void		WriteToPort(LPCTSTR string);     // add by mrlong 2007-12-25
	void        WriteToPort(BYTE* Buffer, int n);// add by mrlong
	void        ClosePort();                     // add by mrlong 2007-12-2  

	void SendData(LPCTSTR lpszData, const int nLength);   //串口发送函数 by mrlong 2008-2-15
	BOOL RecvData(LPTSTR lpszData, const int nSize);      //串口接收函数 by mrlong 2008-2-15

	BOOL SendACK();
	BOOL SendENQ();

protected:
	// protected memberfunctions
	void		ProcessErrorMessage(char* ErrorText);
	static UINT	CommThread(LPVOID pParam);
	static void	ReceiveChar(CSerialPort* port, COMSTAT comstat);
	static void	ReceiveString(CSerialPort* port, COMSTAT comstat); //add by chaochao 2015-12-10
	static void	WriteChar(CSerialPort* port);

	// thread
	CWinThread*			m_Thread;

	// synchronisation objects
	CRITICAL_SECTION	m_csCommunicationSync;
	BOOL				m_bThreadAlive;

	// handles
	HANDLE				m_hShutdownEvent;  //stop发生的事件
	HANDLE				m_hComm;           // read  
	HANDLE				m_hWriteEvent;     // write

	// Event array. 
	// One element is used for each event. There are two event handles for each port.
	// A Write event and a receive character event which is located in the overlapped structure (m_ov.hEvent).
	// There is a general shutdown when the port is closed. 
	HANDLE				m_hEventArray[3];

	// structures
	OVERLAPPED			m_ov;
	COMMTIMEOUTS		m_CommTimeouts;
	DCB					m_dcb;

	// owner window
	CWnd*				m_pOwner;

	// misc
	UINT				m_nPortNr;        //
	char*				m_szWriteBuffer;
	DWORD				m_dwCommEvents;
	DWORD				m_nWriteBufferSize;

	int                 m_nWriteSize; //add by mrlong 2007-12-25
};

#endif __SERIALPORT_H__

CSerialPort.cpp

/*
**	FILENAME			CSerialPort.cpp
**
**	PURPOSE				This class can read, write and watch one serial port.
**						It sends messages to its owner when something happends on the port
**						The class creates a thread for reading and writing so the main
**						program is not blocked.
**
**	CREATION DATE		15-09-1997
**	LAST MODIFICATION	12-11-1997
**
**	AUTHOR				Remon Spekreijse
**
**
*/

#include "stdafx.h"
#include "CSerialPort.h"

#include <assert.h>

//
// Constructor
//
CSerialPort::CSerialPort()
{
	m_hComm = NULL;

	// initialize overlapped structure members to zero
	m_ov.Offset = 0;
	m_ov.OffsetHigh = 0;

	// create events
	m_ov.hEvent = NULL;
	m_hWriteEvent = NULL;
	m_hShutdownEvent = NULL;

	m_szWriteBuffer = NULL;

	m_bThreadAlive = FALSE;
	m_nWriteSize = 1;
}

//
// Delete dynamic memory
//
CSerialPort::~CSerialPort()
{
	do
	{
		SetEvent(m_hShutdownEvent);
	} while (m_bThreadAlive);

	if (m_hComm != NULL)
	{
		CloseHandle(m_hComm);
		m_hComm = NULL;
	}
	// Close Handles  
	if(m_hShutdownEvent!=NULL)
		CloseHandle( m_hShutdownEvent); 
	if(m_ov.hEvent!=NULL)
		CloseHandle( m_ov.hEvent ); 
	if(m_hWriteEvent!=NULL)
		CloseHandle( m_hWriteEvent ); 

	TRACE("Thread ended\n");

	delete [] m_szWriteBuffer;
}

//
// Initialize the port. This can be port 1 to 4.
//
//
//parity:
//  n=none
//  e=even
//  o=odd
//  m=mark
//  s=space
//data:
//  5,6,7,8
//stop:
//  1,1.5,2 
//
BOOL CSerialPort::InitPort(CWnd* pPortOwner,	// the owner (CWnd) of the port (receives message)
						   UINT  portnr,		// portnumber (1..4)
						   UINT  baud,			// baudrate
						   char  parity,		// parity 
						   UINT  databits,		// databits 
						   UINT  stopbits,		// stopbits 
						   DWORD dwCommEvents,	// EV_RXCHAR, EV_CTS etc
						   UINT  writebuffersize,// size to the writebuffer
						   
						   DWORD   ReadIntervalTimeout,
						   DWORD   ReadTotalTimeoutMultiplier,
						   DWORD   ReadTotalTimeoutConstant,
						   DWORD   WriteTotalTimeoutMultiplier,
						   DWORD   WriteTotalTimeoutConstant )	

{
	assert(portnr > 0 && portnr < 8);
	assert(pPortOwner != NULL);

	// if the thread is alive: Kill
	if (m_bThreadAlive)
	{
		do
		{
			SetEvent(m_hShutdownEvent);
		} while (m_bThreadAlive);
		TRACE("Thread ended\n");
	}

	// create events
	if (m_ov.hEvent != NULL)
		ResetEvent(m_ov.hEvent);
	else
		m_ov.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

	if (m_hWriteEvent != NULL)
		ResetEvent(m_hWriteEvent);
	else
		m_hWriteEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
	
	if (m_hShutdownEvent != NULL)
		ResetEvent(m_hShutdownEvent);
	else
		m_hShutdownEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

	// initialize the event objects
	m_hEventArray[0] = m_hShutdownEvent;	// highest priority
	m_hEventArray[1] = m_ov.hEvent;
	m_hEventArray[2] = m_hWriteEvent;

	// initialize critical section
	InitializeCriticalSection(&m_csCommunicationSync);
	
	// set buffersize for writing and save the owner
	m_pOwner = pPortOwner;

	if (m_szWriteBuffer != NULL)
		delete [] m_szWriteBuffer;
	m_szWriteBuffer = new char[writebuffersize];

	m_nPortNr = portnr;

	m_nWriteBufferSize = writebuffersize;
	m_dwCommEvents = dwCommEvents;

	BOOL bResult = FALSE;
	char *szPort = new char[50];
	char *szBaud = new char[50];

	// now it critical!
	EnterCriticalSection(&m_csCommunicationSync);

	// if the port is already opened: close it
	if (m_hComm != NULL)
	{
		CloseHandle(m_hComm);
		m_hComm = NULL;
	}

	// prepare port strings
	sprintf(szPort, "COM%d", portnr);
	// stop is index 0 = 1 1=1.5 2=2
	int mystop;
	int myparity;
	switch(stopbits)
	{
		case 0:
			mystop = ONESTOPBIT;
			break;
		case 1:
			mystop = ONE5STOPBITS;
			break;
		case 2:
			mystop = TWOSTOPBITS;
			break;
	}
	myparity = 0;
	switch(parity)
	{
		case 'N':
			myparity = 0;
			break;
		case 'E':
			myparity = 1;
			break;
		case 'O':
			myparity = 2;
			break;
		case 'M':
			myparity = 3;
			break;
		case 'S':
			myparity = 4;
			break;
	}
	sprintf(szBaud, "baud=%d parity=%c data=%d stop=%d", baud, parity, databits, mystop);

	// get a handle to the port
	m_hComm = CreateFile(szPort,						// communication port string (COMX)
					     GENERIC_READ | GENERIC_WRITE,	// read/write types
					     0,								// comm devices must be opened with exclusive access
					     NULL,							// no security attributes
					     OPEN_EXISTING,					// comm devices must use OPEN_EXISTING
					     FILE_FLAG_OVERLAPPED,			// Async I/O
					     0);							// template must be 0 for comm devices

	if (m_hComm == INVALID_HANDLE_VALUE)
	{
		// port not found
		delete [] szPort;
		delete [] szBaud;

		return FALSE;
	}

	// set the timeout values
	m_CommTimeouts.ReadIntervalTimeout         = ReadIntervalTimeout * 1000;
	m_CommTimeouts.ReadTotalTimeoutMultiplier  = ReadTotalTimeoutMultiplier * 1000;
	m_CommTimeouts.ReadTotalTimeoutConstant    = ReadTotalTimeoutConstant * 1000;
	m_CommTimeouts.WriteTotalTimeoutMultiplier = WriteTotalTimeoutMultiplier * 1000;
	m_CommTimeouts.WriteTotalTimeoutConstant   = WriteTotalTimeoutConstant * 1000;

	// configure
	if (SetCommTimeouts(m_hComm, &m_CommTimeouts))
	{						   
		if (SetCommMask(m_hComm, dwCommEvents))
		{
			if (GetCommState(m_hComm, &m_dcb))
			{
				m_dcb.EvtChar = 'q';
				m_dcb.fRtsControl = RTS_CONTROL_ENABLE;		// set RTS bit high!
				m_dcb.BaudRate = baud;  // add by mrlong
				m_dcb.Parity   = myparity;
				m_dcb.ByteSize = databits;
				m_dcb.StopBits = mystop;
						
				//if (BuildCommDCB(szBaud, &m_dcb))
				//{
					if (SetCommState(m_hComm, &m_dcb))
					{
						// normal operation... continue
					}
					else
					{
						ProcessErrorMessage("SetCommState()");
					}
				//}
				//else
				//	ProcessErrorMessage("BuildCommDCB()");
			}
			else
				ProcessErrorMessage("GetCommState()");
		}
		else
			ProcessErrorMessage("SetCommMask()");
	}
	else
		ProcessErrorMessage("SetCommTimeouts()");

	delete [] szPort;
	delete [] szBaud;

	// flush the port
	PurgeComm(m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);

	// release critical section
	LeaveCriticalSection(&m_csCommunicationSync);

	TRACE("Initialisation for communicationport %d completed.\nUse Startmonitor to communicate.\n", portnr);

	return TRUE;
}

//
//  The CommThread Function.
//
UINT CSerialPort::CommThread(LPVOID pParam)
{
	// Cast the void pointer passed to the thread back to
	// a pointer of CSerialPort class
	CSerialPort *port = (CSerialPort*)pParam;
	
	// Set the status variable in the dialog class to
	// TRUE to indicate the thread is running.
	port->m_bThreadAlive = TRUE;	
		
	// Misc. variables
	DWORD BytesTransfered = 0; 
	DWORD Event = 0;
	DWORD CommEvent = 0;
	DWORD dwError = 0;
	COMSTAT comstat;

	memset(&comstat, 0, sizeof(COMSTAT)); //initial comstate 2015-11-21 chaochao
	BOOL  bResult = TRUE;
		
	// Clear comm buffers at startup
	if (port->m_hComm)		// check if the port is opened
		PurgeComm(port->m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);

	// begin forever loop.  This loop will run as long as the thread is alive.
	for (;;) 
	{ 

		// Make a call to WaitCommEvent().  This call will return immediatly
		// because our port was created as an async port (FILE_FLAG_OVERLAPPED
		// and an m_OverlappedStructerlapped structure specified).  This call will cause the 
		// m_OverlappedStructerlapped element m_OverlappedStruct.hEvent, which is part of the m_hEventArray to 
		// be placed in a non-signeled state if there are no bytes available to be read,
		// or to a signeled state if there are bytes available.  If this event handle 
		// is set to the non-signeled state, it will be set to signeled when a 
		// character arrives at the port.

		// we do this for each port!

		bResult = WaitCommEvent(port->m_hComm, &Event, &port->m_ov);

		if (!bResult)  
		{ 
			// If WaitCommEvent() returns FALSE, process the last error to determin
			// the reason..
			switch (dwError = GetLastError()) 
			{ 
			case ERROR_IO_PENDING: 	
				{ 
					// This is a normal return value if there are no bytes
					// to read at the port.
					// Do nothing and continue
					break;
				}
			case 87:
				{
					// Under Windows NT, this value is returned for some reason.
					// I have not investigated why, but it is also a valid reply
					// Also do nothing and continue.
					break;
				}
			default:
				{
					// All other error codes indicate a serious error has
					// occured.  Process this error.
					port->ProcessErrorMessage("WaitCommEvent()");
					break;
				}
			}
		}
		else
		{
			// If WaitCommEvent() returns TRUE, check to be sure there are
			// actually bytes in the buffer to read.  
			//
			// If you are reading more than one byte at a time from the buffer 
			// (which this program does not do) you will have the situation occur 
			// where the first byte to arrive will cause the WaitForMultipleObjects() 
			// function to stop waiting.  The WaitForMultipleObjects() function 
			// resets the event handle in m_OverlappedStruct.hEvent to the non-signelead state
			// as it returns.  
			//
			// If in the time between the reset of this event and the call to 
			// ReadFile() more bytes arrive, the m_OverlappedStruct.hEvent handle will be set again
			// to the signeled state. When the call to ReadFile() occurs, it will 
			// read all of the bytes from the buffer, and the program will
			// loop back around to WaitCommEvent().
			// 
			// At this point you will be in the situation where m_OverlappedStruct.hEvent is set,
			// but there are no bytes available to read.  If you proceed and call
			// ReadFile(), it will return immediatly due to the async port setup, but
			// GetOverlappedResults() will not return until the next character arrives.
			//
			// It is not desirable for the GetOverlappedResults() function to be in 
			// this state.  The thread shutdown event (event 0) and the WriteFile()
			// event (Event2) will not work if the thread is blocked by GetOverlappedResults().
			//
			// The solution to this is to check the buffer with a call to ClearCommError().
			// This call will reset the event handle, and if there are no bytes to read
			// we can loop back through WaitCommEvent() again, then proceed.
			// If there are really bytes to read, do nothing and proceed.
		
			bResult = ClearCommError(port->m_hComm, &dwError, &comstat);

			if (comstat.cbInQue == 0)
				continue;
			//没有输入
		}	// end if bResult

		// Main wait function.  This function will normally block the thread
		// until one of nine events occur that require action.
		Event = WaitForMultipleObjects(3, port->m_hEventArray, FALSE, INFINITE);
		
		switch (Event)
		{
		case 0:
			{
				// Shutdown event.  This is event zero so it will be
				// the higest priority and be serviced first.

			 	port->m_bThreadAlive = FALSE;
				
				// Kill this thread.  break is not needed, but makes me feel better.
				AfxEndThread(100);
				break;
			}
		case 1:	// read event
			{
				GetCommMask(port->m_hComm, &CommEvent);
				if (CommEvent & EV_RXCHAR) //接收到字符,并置于输入缓冲区中 
					//ReceiveChar(port, comstat);
					//AfxMessageBox("Receive char");
					ReceiveString(port, comstat);
				
				if (CommEvent & EV_CTS) //CTS信号状态发生变化
					::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_CTS_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
				if (CommEvent & EV_RXFLAG) //接收到事件字符,并置于输入缓冲区中 
					::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_RXFLAG_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
				if (CommEvent & EV_BREAK)  //输入中发生中断
					::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_BREAK_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
				if (CommEvent & EV_ERR) //发生线路状态错误,线路状态错误包括CE_FRAME,CE_OVERRUN和CE_RXPARITY 
					::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_ERR_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
				if (CommEvent & EV_RING) //检测到振铃指示
					::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_RING_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
					
				break;
			}  
		case 2: // write event
			{
				// Write character event from port
				WriteChar(port);
				break;
			}

		} // end switch

	} // close forever loop

	return 0;
}

//
// start comm watching
//
BOOL CSerialPort::StartMonitoring()
{
	if (!(m_Thread = AfxBeginThread(CommThread, this)))
		return FALSE;
	TRACE("Thread started\n");
	return TRUE;	
}

//
// Restart the comm thread
//
BOOL CSerialPort::RestartMonitoring()
{
	TRACE("Thread resumed\n");
	m_Thread->ResumeThread();
	return TRUE;	
}


//
// Suspend the comm thread
//
BOOL CSerialPort::StopMonitoring()
{
	TRACE("Thread suspended\n");
	m_Thread->SuspendThread(); 
	return TRUE;	
}


//
// If there is a error, give the right message
//
void CSerialPort::ProcessErrorMessage(char* ErrorText)
{
	char *Temp = new char[200];
	
	LPVOID lpMsgBuf;

	FormatMessage( 
		FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
		NULL,
		GetLastError(),
		MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
		(LPTSTR) &lpMsgBuf,
		0,
		NULL 
	);

	sprintf(Temp, "WARNING:  %s Failed with the following error: \n%s\nPort: %d\n", (char*)ErrorText, lpMsgBuf, m_nPortNr); 
	MessageBox(NULL, Temp, "Application Error", MB_ICONSTOP);

	LocalFree(lpMsgBuf);
	delete[] Temp;
}

//
// Write a character.
//
void CSerialPort::WriteChar(CSerialPort* port)
{
	BOOL bWrite = TRUE;
	BOOL bResult = TRUE;

	DWORD BytesSent = 0;
	DWORD SendLen   = port->m_nWriteSize;
	ResetEvent(port->m_hWriteEvent);


	// Gain ownership of the critical section
	EnterCriticalSection(&port->m_csCommunicationSync);

	if (bWrite)
	{
		// Initailize variables
		port->m_ov.Offset = 0;
		port->m_ov.OffsetHigh = 0;
     
		// Clear buffer
		PurgeComm(port->m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);

		bResult = WriteFile(port->m_hComm,							// Handle to COMM Port
							port->m_szWriteBuffer,					// Pointer to message buffer in calling finction
							SendLen,    // add by mrlong
							//strlen((char*)port->m_szWriteBuffer),	// Length of message to send
							&BytesSent,								// Where to store the number of bytes sent
							&port->m_ov);							// Overlapped structure

		// deal with any error codes
		if (!bResult)  
		{
			DWORD dwError = GetLastError();
			switch (dwError)
			{
				case ERROR_IO_PENDING:
					{
						// continue to GetOverlappedResults()
						BytesSent = 0;
						bWrite = FALSE;
						break;
					}
				default:
					{
						// all other error codes
						port->ProcessErrorMessage("WriteFile()");
					}
			}
		} 
		else
		{
			LeaveCriticalSection(&port->m_csCommunicationSync);
		}
	} // end if(bWrite)

	if (!bWrite)
	{
		bWrite = TRUE;
	
		bResult = GetOverlappedResult(port->m_hComm,	// Handle to COMM port 
									  &port->m_ov,		// Overlapped structure
									  &BytesSent,		// Stores number of bytes sent
									  TRUE); 			// Wait flag

		LeaveCriticalSection(&port->m_csCommunicationSync);

		// deal with the error code 
		if (!bResult)  
		{
			port->ProcessErrorMessage("GetOverlappedResults() in WriteFile()");
		}	
	} // end if (!bWrite)

	// Verify that the data size send equals what we tried to send
	if (BytesSent != SendLen /*strlen((char*)port->m_szWriteBuffer)*/)  // add by 
	{
		TRACE("WARNING: WriteFile() error.. Bytes Sent: %d; Message Length: %d\n", BytesSent, strlen((char*)port->m_szWriteBuffer));
	}
}

//
// Character received. Inform the owner
//
void CSerialPort::ReceiveChar(CSerialPort* port, COMSTAT comstat)
{
	BOOL  bRead = TRUE; 
	BOOL  bResult = TRUE;
	DWORD dwError = 0;
	DWORD BytesRead = 0;
	unsigned char RXBuff;

	for (;;) 
	{ 
        //add by liquanhai 2011-11-06  防止死锁
        if(WaitForSingleObject(port->m_hShutdownEvent,0)==WAIT_OBJECT_0)
      return;

                // Gain ownership of the comm port critical section.
		// This process guarantees no other part of this program 
		// is using the port object. 
		
		EnterCriticalSection(&port->m_csCommunicationSync);

		// ClearCommError() will update the COMSTAT structure and
		// clear any other errors.
		
		bResult = ClearCommError(port->m_hComm, &dwError, &comstat);

		LeaveCriticalSection(&port->m_csCommunicationSync);

		// start forever loop.  I use this type of loop because I
		// do not know at runtime how many loops this will have to
		// run. My solution is to start a forever loop and to
		// break out of it when I have processed all of the
		// data available.  Be careful with this approach and
		// be sure your loop will exit.
		// My reasons for this are not as clear in this sample 
		// as it is in my production code, but I have found this 
		// solutiion to be the most efficient way to do this.
		
		if (comstat.cbInQue == 0)
		{
			// break out when all bytes have been read
			break;
		}
						
		EnterCriticalSection(&port->m_csCommunicationSync);

		if (bRead)
		{
			bResult = ReadFile(port->m_hComm,		// Handle to COMM port 
							   &RXBuff,				// RX Buffer Pointer
							   1,					// Read one byte
							   &BytesRead,			// Stores number of bytes read
							   &port->m_ov);		// pointer to the m_ov structure
			// deal with the error code 
			if (!bResult)  
			{ 
				switch (dwError = GetLastError()) 
				{ 
					case ERROR_IO_PENDING: 	
						{ 
							// asynchronous i/o is still in progress 
							// Proceed on to GetOverlappedResults();
							bRead = FALSE;
							break;
						}
					default:
						{
							// Another error has occured.  Process this error.
							port->ProcessErrorMessage("ReadFile()");
							break;
						} 
				}
			}
			else
			{
				// ReadFile() returned complete. It is not necessary to call GetOverlappedResults()
				bRead = TRUE;
			}
		}  // close if (bRead)

		if (!bRead)
		{
			bRead = TRUE;
			bResult = GetOverlappedResult(port->m_hComm,	// Handle to COMM port 
										  &port->m_ov,		// Overlapped structure
										  &BytesRead,		// Stores number of bytes read
										  TRUE); 			// Wait flag

			// deal with the error code 
			if (!bResult)  
			{
				port->ProcessErrorMessage("GetOverlappedResults() in ReadFile()");
			}	
		}  // close if (!bRead)
				
		LeaveCriticalSection(&port->m_csCommunicationSync);

		// notify parent that a byte was received
		::SendMessage((port->m_pOwner)->m_hWnd, WM_COMM_RXCHAR, (WPARAM) RXBuff, (LPARAM) port->m_nPortNr);
	} // end forever loop

}



//
// Character received. Inform the owner
//
void CSerialPort::ReceiveString(CSerialPort* port, COMSTAT comstat)
{
	BOOL  bRead = TRUE; 
	BOOL  bResult = TRUE;
	DWORD dwError = 0;
	DWORD BytesRead = 0;
	
	unsigned char RXBuff;

	for (;;) 
	{ 
        //add by liquanhai 2011-11-06  防止死锁
        if(WaitForSingleObject(port->m_hShutdownEvent,0)==WAIT_OBJECT_0)
      return;

                // Gain ownership of the comm port critical section.
		// This process guarantees no other part of this program 
		// is using the port object. 
		
		EnterCriticalSection(&port->m_csCommunicationSync);

		// ClearCommError() will update the COMSTAT structure and
		// clear any other errors.
		
		bResult = ClearCommError(port->m_hComm, &dwError, &comstat);

		LeaveCriticalSection(&port->m_csCommunicationSync);

		// start forever loop.  I use this type of loop because I
		// do not know at runtime how many loops this will have to
		// run. My solution is to start a forever loop and to
		// break out of it when I have processed all of the
		// data available.  Be careful with this approach and
		// be sure your loop will exit.
		// My reasons for this are not as clear in this sample 
		// as it is in my production code, but I have found this 
		// solutiion to be the most efficient way to do this.
		
		if (comstat.cbInQue == 0)
		{
			// break out when all bytes have been read
			break;
		}
		//CString str1;
		//str1.Format("%d",comstat.cbInQue);
		//AfxMessageBox(str1);

		char* readBuff=new char[comstat.cbInQue];
		
						
		EnterCriticalSection(&port->m_csCommunicationSync);

		if (bRead)
		{
			
			bResult = ReadFile(port->m_hComm,		// Handle to COMM port 
							   readBuff,				// RX Buffer Pointer
							   comstat.cbInQue,					// Read one byte
							   &BytesRead,			// Stores number of bytes read
							   &port->m_ov);		// pointer to the m_ov structure
			// deal with the error code 
			if (!bResult)  
			{ 
				
				switch (dwError = GetLastError()) 
				{ 
					case ERROR_IO_PENDING: 	
						{ 
							// asynchronous i/o is still in progress 
							// Proceed on to GetOverlappedResults();
							AfxMessageBox("ERROR_IO_PENDING");
							bRead = FALSE;
							break;
						}
					default:
						{
							// Another error has occured.  Process this error.
							
							port->ProcessErrorMessage("ReadFile()");
							break;
						} 
				}
			}
			else
			{
				// ReadFile() returned complete. It is not necessary to call GetOverlappedResults()
				
				bRead = TRUE;
			}
		}  // close if (bRead)

		if (!bRead)
		{
			bRead = TRUE;
			bResult = GetOverlappedResult(port->m_hComm,	// Handle to COMM port 
										  &port->m_ov,		// Overlapped structure
										  &BytesRead,		// Stores number of bytes read
										  TRUE); 			// Wait flag
			
			// deal with the error code 

			if (!bResult)  
			{
				port->ProcessErrorMessage("GetOverlappedResults() in ReadFile()");
			}	
		}  // close if (!bRead)
				
		LeaveCriticalSection(&port->m_csCommunicationSync);

		// notify parent that a byte was received
		
		
		
		::SendMessage((port->m_pOwner)->m_hWnd, WM_COMM_RECEIVE_STRING, (WPARAM) readBuff, (LPARAM) BytesRead);
	} // end forever loop

}


//
// Write a string to the port
//
void CSerialPort::WriteToPort(char* string)
{		
	assert(m_hComm != 0);

	memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer));
	strcpy(m_szWriteBuffer, string);
	m_nWriteSize=strlen(string); // add by mrlong
	// set event for write
	SetEvent(m_hWriteEvent);
}

//
// Return the device control block
//
DCB CSerialPort::GetDCB()
{
	return m_dcb;
}

//
// Return the communication event masks
//
DWORD CSerialPort::GetCommEvents()
{
	return m_dwCommEvents;
}

//
// Return the output buffer size
//
DWORD CSerialPort::GetWriteBufferSize()
{
	return m_nWriteBufferSize;
}

void CSerialPort::ClosePort()
{
        MSG message;
	do
	{
	      SetEvent(m_hShutdownEvent);
		if(::PeekMessage(&message,m_pOwner->m_hWnd,0,0,PM_REMOVE))
		{
		::TranslateMessage(&message);
		 ::DispatchMessage(&message);
		}
               
         } while (m_bThreadAlive);

	// if the port is still opened: close it 
	if (m_hComm != NULL)
	{
		CloseHandle(m_hComm);
		m_hComm = NULL;
	}
	
	// Close Handles  
	if(m_hShutdownEvent!=NULL)
		ResetEvent(m_hShutdownEvent);
	if(m_ov.hEvent!=NULL)
		ResetEvent(m_ov.hEvent);
	if(m_hWriteEvent!=NULL)
		ResetEvent(m_hWriteEvent);			
		
	//delete [] m_szWriteBuffer;
	
}

void CSerialPort::WriteToPort(char* string,int n)
{
	assert(m_hComm != 0);
	memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer));
	memcpy(m_szWriteBuffer, string, n);
	m_nWriteSize = n;

	// set event for write
	SetEvent(m_hWriteEvent);
}

void CSerialPort::WriteToPort(LPCTSTR string)
{
	assert(m_hComm != 0);
	memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer));
	strcpy(m_szWriteBuffer, string);
	m_nWriteSize=strlen(string);
	// set event for write
	SetEvent(m_hWriteEvent);
}

void CSerialPort::WriteToPort(BYTE* Buffer, int n)
{
	assert(m_hComm != 0);
	memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer));
	int i;
	for(i=0; i<n; i++)
	{
		m_szWriteBuffer[i] = Buffer[i];
	}
	m_nWriteSize=n;

	// set event for write
	SetEvent(m_hWriteEvent);
}


void CSerialPort::SendData(LPCTSTR lpszData, const int nLength)
{
	assert(m_hComm != 0);
	if(m_szWriteBuffer!=NULL)
	{
		delete m_szWriteBuffer;
	}
	m_szWriteBuffer=new char[nLength];
	m_nWriteSize=nLength;
	strncpy(m_szWriteBuffer, lpszData,nLength);
	//memset(m_szWriteBuffer, 0, nLength);
	//strcpy(m_szWriteBuffer, lpszData);
	//m_nWriteSize=nLength;
	// set event for write

	SetEvent(m_hWriteEvent);
}

BOOL CSerialPort::RecvData(LPTSTR lpszData, const int nSize)
{
	//
	//接收数据
	//
	assert(m_hComm!=0);
	memset(lpszData,0,nSize);
	int mylen  = 0;
	DWORD mylen2 = 0;
	while (mylen < nSize) {
		if(!ReadFile(m_hComm,lpszData,nSize,&mylen2,NULL)) 
			return FALSE;
		mylen += mylen2;

		
	}
	
	return TRUE;
}

BOOL CSerialPort::SendACK()
{
	

	assert(m_hComm != 0);
	memset(m_szWriteBuffer, 0, 1);
	m_szWriteBuffer[0]=6;
	m_nWriteSize=1;
	// set event for write
	SetEvent(m_hWriteEvent);
	
	return TRUE;
}

BOOL CSerialPort::SendENQ()
{
	

	assert(m_hComm != 0);
	memset(m_szWriteBuffer, 0, 1);
	m_szWriteBuffer[0]=5;
	m_nWriteSize=1;
	// set event for write
	SetEvent(m_hWriteEvent);
	
	return TRUE;
}

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3条回应:“解决CSerialPort串口通讯类单字符接收的问题”

  1. 好书网说道:

    过来看看

  2. 痴海说道:

    谢谢啦,很有用!

  3. 家具电商说道:

    [真美好] 很用心的說明~~~謝謝老实~~~

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