怎么知道哪个COM口对应GSM？

Question

我编写在Mobile手机上运行的程序。

我要使用CreateFile打开GSM对应的COM口读写，可是怎么知道哪个口是对应GSM呢？
另外，打开COM口，写入“AT\r\n”之后，怎么没有反应，不是应该返回AT或者OK的吗？

Answer 1

There are my codes below, any mistakes?

 wchar_t Buff[36];
 char CharBuff[256];
 COMMTIMEOUTS ctos;
 DCB dcb;
  wsprintf(Buff, L"COM%d:", 4);//my GSM is COM4
  HANDLE hFile = CreateFile(Buff, GENERIC_WRITE | GENERIC_READ, 0, NULL, OPEN_EXISTING, 0, NULL);
  if(hFile != INVALID_HANDLE_VALUE)
  {
   if(!GetCommState(hFile, &dcb))
   {
    outputMsgIntoFile("GetCommState failed, error code is 0x%X\n", GetLastError());
    CloseHandle(hFile);
    return;
   }
   //PrintDCB(&dcb);
   dcb.BaudRate = CBR_9600;
   dcb.ByteSize = 8;
   dcb.Parity = NOPARITY;
   dcb.fParity = FALSE;
   dcb.StopBits = ONESTOPBIT;
   dcb.fBinary = TRUE;
   dcb.fDtrControl = 0; 
   dcb.fRtsControl = 0;
   dcb.fOutX = 0;
   dcb.fInX = 0;
   dcb.fTXContinueOnXoff = 0;
   SetupComm(hFile, 512, 512);
   if(!SetCommState(hFile, &dcb))
   {
    outputMsgIntoFile("SetCommState failed, error code is 0x%X\n", GetLastError());
    CloseHandle(hFile);
    return;
   }

   outputMsgIntoFile("COM opened.\n");
   ctos.ReadIntervalTimeout = MAXDWORD;
   ctos.ReadTotalTimeoutMultiplier = 0;
   ctos.ReadTotalTimeoutConstant = 0;
   ctos.WriteTotalTimeoutConstant = 5;
   ctos.WriteTotalTimeoutMultiplier = 5;
   if(!SetCommTimeouts(hFile, &ctos))
   {
    outputMsgIntoFile("SetCommTimeouts failed, error code is 0x%X\n", GetLastError());
    CloseHandle(hFile);
    return;
   }
   outputMsgIntoFile("SetCommTimeouts done");
   sprintf(CharBuff, "AT\r\n");
   DWORD dwWritten;
   if(!WriteFile(hFile, &CharBuff[0], strlen(CharBuff), &dwWritten, NULL))
   {
    outputMsgIntoFile("WriteFile failed, error code is 0x%X\n", GetLastError());
    CloseHandle(hFile);
    return;
   }
   outputMsgIntoFile("WriteFile OK");
   DWORD dwRead;
   memset(&CharBuff[0], 0, 256);

   Sleep(15000);

   DWORD dwErrorFlags;
   COMSTAT ComStat ;
   
   ClearCommError(hFile, &dwErrorFlags, &ComStat );
   if(ComStat.cbInQue)
   {
    if(!ReadFile(hFile, &CharBuff[0], (ComStat.cbInQue > 200) ? 200 : ComStat.cbInQue, &dwRead, NULL))
    {
     outputMsgIntoFile("ReadFile failed, error code is 0x%X\n", GetLastError());
     CloseHandle(hFile);
     return;
    }
    outputMsgIntoFile("ReadFile OK, got:%s", CharBuff);
   }
   else
   {
    outputMsgIntoFile("no data");
   }
   CloseHandle(hFile);
  }
  else
  {
   outputMsgIntoFile("Can not opened");
  }

Answer 2

你好，

可以参考英文论坛的这个帖子，里面给出了一些建议：

connect to internal modem

Starting With a GSM Modem Application

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施炯