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;
  }
 }
}