在C#中实现串口通信的方法

通常，在C#中实现串口通信，我们有四种方法：
第一：通过MSCOMM控件这是最简单的，最方便的方法。可功能上很难做到控制自如，同时这个控件并不是系统本身所带，所以还得注册，不在本文讨论范围。可以访问http://www.devhood.com/tutorials/tutorial_details.aspx?tutorial_id=320 ，一个国外网友的写的教程，作者很热心，我曾有发邮件给他，很快就回复了。

第二：微软在.NET新推出了一个串口控件，基于.NET的P/Invoke调用方法实现，详细的大家可以访问微软网站http://msdn.microsoft.com/msdnmag/issues/02/10/NETSerialComm/default.aspx，方便得到更多资料。

第三：就是用第三方控件啦，可一般都要付费的，不太合实际，不作考虑

第四：自己用API写串口通信，这样难度高点，但对于我们来说，可以方便实现自己想要的各种功能

在本文，我们采用第四种方法来实现串口通信，不过不是自己写，用一个国外网友现成的已经封装好的类库，不过功能简单点，相对我们来说已经够用了。

在整个终端短信的操作过程中，与串口的通信，只用到了四个功能，打开、写、读、关闭串口。下面是类库对这四个功能的定义：

打开串口：

函数原型：public void Open()

说明：打开事先设置好的端口

示例：

using JustinIO;

static JustinIO.CommPort ss_port = new JustinIO.CommPort();
ss_port.PortNum = COM1; //端口号
ss_port.BaudRate = 19200; //串口通信波特率
ss_port.ByteSize = 8; //数据位
ss_port.Parity = 0; //奇偶校验
ss_port.StopBits = 1;//停止位
ss_port.ReadTimeout = 1000; //读超时
try
{
　if (ss_port.Opened)
　{
　　ss_port.Close();
　　ss_port.Open(); //打开串口
　}
　else
　{
　　ss_port.Open();//打开串口
　}
　return true;
}
catch(Exception e)
{
　MessageBox.Show("错误：" + e.Message);
　return false;
}

写串口：

函数原型：public void Write(byte[] WriteBytes)

WriteBytes 就是你的写入的字节，注意，字符串要转换成字节数组才能进行通信

示例：

ss_port.Write(Encoding.ASCII.GetBytes("AT+CGMI\r")); //获取手机品牌

读串口：

函数原型：public byte[] Read(int NumBytes)

NumBytes 读入缓存数，注意读取来的是字节数组，要实际应用中要进行字符转换

示例：

string response = Encoding.ASCII.GetString(ss_port.Read(128)); //读取128个字节缓存

关闭串口：

函数原型：ss_port.Close()

示例：

ss_port.Close();

由于篇幅，以及串口通信涉及内容广泛，我在这里只讲这些。

在上面我们已经把终端短信所需的各种原始技术有所了解，是可以小试牛刀的时候了。

using System;
using System.Runtime.InteropServices;

namespace BusApp
{
/// <summary>
///
/// </summary>
public class mycom
{
public mycom()
{
//
// TODO: 在此处添加构造函数逻辑
//
}
public int PortNum; //1,2,3,4
public int BaudRate; //1200,2400,4800,9600
public byte ByteSize; //8 bits
public byte Parity; // 0-4=no,odd,even,mark,space
public byte StopBits; // 0,1,2 = 1, 1.5, 2
public int ReadTimeout; //10

//comm port win32 file handle
private int hComm = -1;

public bool Opened = false;

//win32 api constants
private const uint GENERIC_READ = 0x80000000;
private const uint GENERIC_WRITE = 0x40000000;
private const int OPEN_EXISTING = 3;
private const int INVALID_HANDLE_VALUE = -1;

[StructLayout(LayoutKind.Sequential)]
private struct DCB
{
//taken from c struct in platform sdk
public int DCBlength;           // sizeof(DCB)
public int BaudRate;            // current baud rate
public int fBinary;          // binary mode, no EOF check
public int fParity;          // enable parity checking
public int fOutxCtsFlow;      // CTS output flow control
public int fOutxDsrFlow;      // DSR output flow control
public int fDtrControl;       // DTR flow control type
public int fDsrSensitivity;   // DSR sensitivity
public int fTXContinueOnXoff; // XOFF continues Tx
public int fOutX;          // XON/XOFF out flow control
public int fInX;           // XON/XOFF in flow control
public int fErrorChar;     // enable error replacement
public int fNull;          // enable null stripping
public int fRtsControl;     // RTS flow control
public int fAbortOnError;   // abort on error
public int fDummy2;        // reserved
public ushort wReserved;          // not currently used
public ushort XonLim;             // transmit XON threshold
public ushort XoffLim;            // transmit XOFF threshold
public byte ByteSize;           // number of bits/byte, 4-8
public byte Parity;             // 0-4=no,odd,even,mark,space
public byte StopBits;           // 0,1,2 = 1, 1.5, 2
public char XonChar;            // Tx and Rx XON character
public char XoffChar;           // Tx and Rx XOFF character
public char ErrorChar;          // error replacement character
public char EofChar;            // end of input character
public char EvtChar;            // received event character
public ushort wReserved1;         // reserved; do not use
}

[StructLayout(LayoutKind.Sequential)]
private struct COMMTIMEOUTS
{
public int ReadIntervalTimeout;
public int ReadTotalTimeoutMultiplier;
public int ReadTotalTimeoutConstant;
public int WriteTotalTimeoutMultiplier;
public int WriteTotalTimeoutConstant;
}

[StructLayout(LayoutKind.Sequential)]
private struct OVERLAPPED
{
public int  Internal;
public int  InternalHigh;
public int  Offset;
public int  OffsetHigh;
public int hEvent;
}

[DllImport("kernel32.dll")]
private static extern int CreateFile(
string lpFileName,                         // file name
uint dwDesiredAccess,                      // access mode
int dwShareMode,                          // share mode
int lpSecurityAttributes, // SD
int dwCreationDisposition,                // how to create
int dwFlagsAndAttributes,                 // file attributes
int hTemplateFile                        // handle to template file
);
[DllImport("kernel32.dll")]
private static extern bool GetCommState(
int hFile,  // handle to communications device
ref DCB lpDCB    // device-control block
);
[DllImport("kernel32.dll")]
private static extern bool BuildCommDCB(
string lpDef,  // device-control string
ref DCB lpDCB     // device-control block
);
[DllImport("kernel32.dll")]
private static extern bool SetCommState(
int hFile,  // handle to communications device
ref DCB lpDCB    // device-control block
);
[DllImport("kernel32.dll")]
private static extern bool GetCommTimeouts(
int hFile,                  // handle to comm device
ref COMMTIMEOUTS lpCommTimeouts  // time-out values
);
[DllImport("kernel32.dll")]
private static extern bool SetCommTimeouts(
int hFile,                  // handle to comm device
ref COMMTIMEOUTS lpCommTimeouts  // time-out values
);
[DllImport("kernel32.dll")]
private static extern bool ReadFile(
int hFile,                // handle to file
byte[] lpBuffer,             // data buffer
int nNumberOfBytesToRead,  // number of bytes to read
ref int lpNumberOfBytesRead, // number of bytes read
ref OVERLAPPED lpOverlapped    // overlapped buffer
);
[DllImport("kernel32.dll")]
private static extern bool WriteFile(
int hFile,                    // handle to file
byte[] lpBuffer,                // data buffer
int nNumberOfBytesToWrite,     // number of bytes to write
ref int lpNumberOfBytesWritten,  // number of bytes written
ref OVERLAPPED lpOverlapped        // overlapped buffer
);
[DllImport("kernel32.dll")]
private static extern bool CloseHandle(
int hObject   // handle to object
);

public void Open()
{

DCB dcbCommPort = new DCB();
COMMTIMEOUTS ctoCommPort = new COMMTIMEOUTS();

// OPEN THE COMM PORT.

hComm = CreateFile("COM" + PortNum ,GENERIC_READ | GENERIC_WRITE,0, 0,OPEN_EXISTING,0,0);

// IF THE PORT CANNOT BE OPENED, BAIL OUT.
if(hComm == INVALID_HANDLE_VALUE)
{
throw(new ApplicationException("Comm Port Can Not Be Opened"));
}

// SET THE COMM TIMEOUTS.

GetCommTimeouts(hComm,ref ctoCommPort);
ctoCommPort.ReadTotalTimeoutConstant = ReadTimeout;
ctoCommPort.ReadTotalTimeoutMultiplier = 0;
ctoCommPort.WriteTotalTimeoutMultiplier = 0;
ctoCommPort.WriteTotalTimeoutConstant = 0;
SetCommTimeouts(hComm,ref ctoCommPort);

// SET BAUD RATE, PARITY, WORD SIZE, AND STOP BITS.
// THERE ARE OTHER WAYS OF DOING SETTING THESE BUT THIS IS THE EASIEST.
// IF YOU WANT TO LATER ADD CODE FOR OTHER BAUD RATES, REMEMBER
// THAT THE ARGUMENT FOR BuildCommDCB MUST BE A POINTER TO A STRING.
// ALSO NOTE THAT BuildCommDCB() DEFAULTS TO NO HANDSHAKING.

dcbCommPort.DCBlength = Marshal.SizeOf(dcbCommPort);
GetCommState(hComm, ref dcbCommPort);
dcbCommPort.BaudRate=BaudRate;
dcbCommPort.Parity=Parity;
dcbCommPort.ByteSize=ByteSize;
dcbCommPort.StopBits=StopBits;
SetCommState(hComm, ref dcbCommPort);

Opened = true;

}

public void Close()
{
if (hComm!=INVALID_HANDLE_VALUE)
{
CloseHandle(hComm);
Opened=false;
}
}

public byte[] Read(int NumBytes)
{
byte[] BufBytes;
byte[] OutBytes;
BufBytes = new byte[NumBytes];
if (hComm!=INVALID_HANDLE_VALUE)
{
OVERLAPPED ovlCommPort = new OVERLAPPED();
int BytesRead=0;
ReadFile(hComm,BufBytes,NumBytes,ref BytesRead,ref ovlCommPort);
OutBytes = new byte[BytesRead];
Array.Copy(BufBytes,OutBytes,BytesRead);
}
else
{
throw(new ApplicationException("Comm Port Not Open"));
}
return OutBytes;
}

public int Write(byte[] WriteBytes)
{
int BytesWritten = 0;
if (hComm!=INVALID_HANDLE_VALUE)
{
OVERLAPPED ovlCommPort = new OVERLAPPED();
WriteFile(hComm,WriteBytes,WriteBytes.Length,ref BytesWritten,ref ovlCommPort);
}
else
{
throw(new ApplicationException("Comm Port Not Open"));
}
return BytesWritten;
}
}
}