最近在用Modem进行电话编程，开始使用.net自带的SerialPort类来进行通讯，测试过程中发现一个问题：
环境一： API写的串口工具(Modem1）与API写的串口工具（Modem2)
均已57600,N,8,1的波特率打开，Modem1的电话为8001 ,Modem2的电话为8002 ，
Modem2 发送 ATDT8001\r\n
Modem1 收到 \r\nRing (重复收到)
Modem1 发送 ATA\r\n
Modem1 收到 CONNECT 57600\r\n 同时
Modem2 收到 CONNECT 57600\r\n
至此2个Modem已经正常连接，可进行数据通讯
环境二： c#写的串口工具(Modem1）与API写的串口工具（Modem2)
均已57600,N,8,1的波特率打开，Modem1的电话为8001
,Modem2的电话为8002 ，
Modem2 发送
ATDT8001\r\n
Modem1 收到 \r\nRing (重复收到)
Modem1 发送 ATA\r\n
Modem1 收到 CONNECT 57600\r\n 同时
Modem2 收到 CONNECT 57600\r\n
至此2个Modem已经正常连接
但是通讯时，Modem1发送的数据，Modem2可正常收到，但是Modem2发送的数据，Modem1无法收到
断点SerialPort的DataReceived方法，结果无数据接收,多次试验无果。
分析： 因其他硬件一致，排除硬件原因，感觉像是SerialPort类有问题，因此尝试改用C#
调用API函数打开串 口，结果正常。怀疑SerialPort有Bug。
以下为网上找的API 串口类，自己做了稍微修改，记录下。
///
/// API串口类 叶帆修改
http://blog.csdn.net/yefanqiu
/// 2014.1.4
zyf 修改
///
1.修改了串口参数形式,改为9600,N,8,1格式
/// 2.增加了ClearCommError
API函数,用于获取可读字节数
///
public class
CommPort
{
///
///端口名称(COM1,COM2...COM4...)
///
public string Port = "COM1:";
///
/// 波特率(9600,N,8,1)
///
public string CommSetting = "9600,N,8,1";
///
///超时长
///
public int ReadTimeout = 200;
///
///串口是否已经打开
///
public bool Opened = false;
///
/// COM口句柄
///
private int hComm = -1;
#region "API相关定义"
private const string DLLPATH = "kernel32.dll";
// "kernel32";
///
/// WINAPI常量,写标志
///
private const uint GENERIC_READ =
0x80000000;
///
/// WINAPI常量,读标志
///
private const uint GENERIC_WRITE =
0x40000000;
///
/// WINAPI常量,打开已存在
///
private const int OPEN_EXISTING = 3;
///
/// WINAPI常量,无效句柄
///
private const int INVALID_HANDLE_VALUE =
-1;
private const int PURGE_RXABORT = 0x2;
private const int PURGE_RXCLEAR = 0x8;
private const int PURGE_TXABORT = 0x1;
private const int PURGE_TXCLEAR = 0x4;
///
///设备控制块结构体类型
///
[StructLayout(LayoutKind.Sequential)]
public struct DCB
{
///
///
DCB长度
///
public int
DCBlength;
///
///指定当前波特率
///
public int
BaudRate;
///
///标志位
///
public
uint flags;
///
///未使用,必须为0
///
public
ushort wReserved;
///
///指定在XON字符发送这前接收缓冲区中可允许的最小字节数
///
public
ushort XonLim;
///
///指定在XOFF字符发送这前接收缓冲区中可允许的最小字节数
///
public
ushort XoffLim;
///
///指定端口当前使用的数据位
///
public
byte ByteSize;
///
///指定端口当前使用的奇偶校验方法,可能为:EVENPARITY,MARKPARITY,NOPARITY,ODDPARITY
0-4=no,odd,even,mark,space
///
public
byte Parity;
///
///指定端口当前使用的停止位数,可能为:ONESTOPBIT,ONE5STOPBITS,TWOSTOPBITS 0,1,2 = 1,
1.5, 2
///
public
byte StopBits;
///
///指定用于发送和接收字符XON的值 Tx and Rx XON character
///
public
byte XonChar;
///
///指定用于发送和接收字符XOFF值 Tx and Rx XOFF character
///
public
byte XoffChar;
///
///本字符用来代替接收到的奇偶校验发生错误时的值
///
public
byte ErrorChar;
///
///当没有使用二进制模式时,本字符可用来指示数据的结束
///
public
byte EofChar;
///
///当接收到此字符时,会产生一个事件
///
public
byte EvtChar;
///
///未使用
///
public
ushort wReserved1;
}
///
///串口超时时间结构体类型
///
[StructLayout(LayoutKind.Sequential)]
private struct COMMTIMEOUTS
{
public int
ReadIntervalTimeout;
public int
ReadTotalTimeoutMultiplier;
public int
ReadTotalTimeoutConstant;
public int
WriteTotalTimeoutMultiplier;
public int
WriteTotalTimeoutConstant;
}
///
///溢出缓冲区结构体类型
///
[StructLayout(LayoutKind.Sequential)]
private struct OVERLAPPED
{
public int
Internal;
public int
InternalHigh;
public int
Offset;
public int
OffsetHigh;
public int
hEvent;
}
///
/// ClearCommError的结构
///
private struct COMSTAT
{
internal
const uint fCtsHold = 0x1;
internal
const uint fDsrHold = 0x2;
internal
const uint fRlsdHold = 0x4;
internal
const uint fXoffHold = 0x8;
internal
const uint fXoffSent = 0x10;
internal
const uint fEof = 0x20;
internal
const uint fTxim = 0x40;
internal
UInt32 Flags;
///
///
输入缓存中字节个数
///
public
uint cbInQue;
///
///
输出缓存中字节个数
///
public
uint cbOutQue;
}
///
///打开串口
///
///要打开的串口名称
///指定串口的访问方式，一般设置为可读可写方式
///指定串口的共享模式，串口不能共享，所以设置为0
///设置串口的安全属性，WIN9X下不支持，应设为NULL
///对于串口通信，创建方式只能为OPEN_EXISTING
///指定串口属性与标志，设置为FILE_FLAG_OVERLAPPED(重叠I/O操作)，指定串口以异步方式通信
///对于串口通信必须设置为NULL
[DllImport(DLLPATH)]
private static extern int CreateFile(string
lpFileName, uint dwDesiredAccess, int dwShareMode,
int lpSecurityAttributes, int
dwCreationDisposition, int dwFlagsAndAttributes, int
hTemplateFile);
///
///得到串口状态
///
///通信设备句柄
///设备控制块DCB
[DllImport(DLLPATH)]
private static extern bool GetCommState(int
hFile, ref DCB lpDCB);
///
///建立串口设备控制块(嵌入版没有)
///
///设备控制字符串
///设备控制块
[DllImport(DLLPATH)]
private static extern bool BuildCommDCB(string
lpDef, ref DCB lpDCB);
///
///设置串口状态
///
///通信设备句柄
///设备控制块
[DllImport(DLLPATH)]
private static extern bool SetCommState(int
hFile, ref DCB lpDCB);
///
///读取串口超时时间
///
///通信设备句柄
///超时时间
[DllImport(DLLPATH)]
private static extern bool GetCommTimeouts(int
hFile, ref COMMTIMEOUTS lpCommTimeouts);
///
///设置串口超时时间
///
///通信设备句柄
///超时时间
[DllImport(DLLPATH)]
private static extern bool SetCommTimeouts(int
hFile, ref COMMTIMEOUTS lpCommTimeouts);
///
/// 清除串口错误或者读取串口现在的状态
///
///
///
///
[DllImport(DLLPATH)]
private static extern bool ClearCommError(IntPtr
hFile, ref uint lpErrors,ref COMSTAT lpStat);
///
///读取串口数据
///
///通信设备句柄
///数据缓冲区
///多少字节等待读取
///读取多少字节
///溢出缓冲区
[DllImport(DLLPATH)]
private static extern bool ReadFile(int hFile,
byte[] lpBuffer, int nNumberOfBytesToRead,
ref int lpNumberOfBytesRead, ref OVERLAPPED
lpOverlapped);
///
///写串口数据
///
///通信设备句柄
///数据缓冲区
///多少字节等待写入
///已经写入多少字节
///溢出缓冲区
[DllImport(DLLPATH)]
private static extern bool WriteFile(int hFile,
byte[] lpBuffer, int nNumberOfBytesToWrite,
ref int lpNumberOfBytesWritten, ref OVERLAPPED
lpOverlapped);
[DllImport(DLLPATH, SetLastError = true)]
private static extern bool FlushFileBuffers(int
hFile);
[DllImport(DLLPATH, SetLastError = true)]
private static extern bool PurgeComm(int hFile,
uint dwFlags);
///
///关闭串口
///
///通信设备句柄
[DllImport(DLLPATH)]
private static extern bool CloseHandle(int
hObject);
///
///得到串口最后一次返回的错误
///
[DllImport(DLLPATH)]
private static extern uint GetLastError();
#endregion
///
///设置DCB标志位
///
///
///
///
internal void SetDcbFlag(int whichFlag, int
setting, DCB dcb)
{
uint
num;
setting =
setting << whichFlag;
if
((whichFlag == 4) || (whichFlag == 12))
{
num = 3;
}
else if
(whichFlag == 15)
{
num = 0x1ffff;
}
else
{
num = 1;
}
dcb.flags
&= ~(num << whichFlag);
dcb.flags
|= (uint)setting;
}
///
///建立与串口的连接,返回0为成功,非0为不成功
///
public int Open()
{
DCB dcb =
new DCB();
COMMTIMEOUTS ctoCommPort = new COMMTIMEOUTS();
//
打开串口
hComm =
CreateFile(Port, GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING,
0, 0);
if (hComm
== INVALID_HANDLE_VALUE)
{
return -1;
}
//
设置通信超时时间
GetCommTimeouts(hComm, ref ctoCommPort);
ctoCommPort.ReadTotalTimeoutConstant = ReadTimeout;
ctoCommPort.ReadTotalTimeoutMultiplier = 0;
ctoCommPort.WriteTotalTimeoutMultiplier = 0;
ctoCommPort.WriteTotalTimeoutConstant = 0;
SetCommTimeouts(hComm, ref ctoCommPort);
//设置串口参数
if(
!GetCommState(hComm, ref dcb))
{
return -1;
}
//修改dcb数据,将需要的波特率设置进去
if
(!BuildCommDCB(CommSetting, ref dcb))
{
return -1;
}
//设置波特率
if
(!SetCommState(hComm, ref dcb))
{
return -1;
}
Opened =
true;
return
0;
}
///
///关闭串口,结束通讯
///
public void Close()
{
if (hComm
!= INVALID_HANDLE_VALUE)
{
CloseHandle(hComm);
}
}
///
/// 获取输入缓存中存在的字节数
///
/// 可读字节数 ; 返回 -1 时,出错
public long ByteToRead()
{
if (hComm
!= INVALID_HANDLE_VALUE)
{
COMSTAT lSTAT=new
COMSTAT();
uint lerror=0;
bool f =
ClearCommError((IntPtr)hComm, ref lerror, ref lSTAT);
return lSTAT.cbInQue;
}
else
{
return -1;
}
}
///
///读取串口返回的数据
///
///数据长度
public int Read(ref byte[] bytData, int
NumBytes)
{
if (hComm
!= INVALID_HANDLE_VALUE)
{
OVERLAPPED ovlCommPort = new
OVERLAPPED();
int BytesRead = 0;
ReadFile(hComm, bytData,
NumBytes, ref BytesRead, ref ovlCommPort);
return BytesRead;
}
else
{
return -1;
}
}
///
///向串口写数据
///
///数据数组
public int Write(byte[] WriteBytes, int
intSize)
{
if (hComm
!= INVALID_HANDLE_VALUE)
{
OVERLAPPED ovlCommPort = new
OVERLAPPED();
int BytesWritten = 0;
WriteFile(hComm, WriteBytes,
intSize, ref BytesWritten, ref ovlCommPort);
return BytesWritten;
}
else
{
return -1;
}
}
///
///清除接收缓冲区
///
///
public void ClearReceiveBuf()
{
if (hComm
!= INVALID_HANDLE_VALUE)
{
PurgeComm(hComm,
PURGE_RXABORT | PURGE_RXCLEAR);
}
}
///
///清除发送缓冲区
///
public void ClearSendBuf()
{
if (hComm
!= INVALID_HANDLE_VALUE)
{
PurgeComm(hComm,
PURGE_TXABORT | PURGE_TXCLEAR);
}
}
}
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