获取PC可用串口端口，并将其在combo box中显示

通常应用中，我会遇到需要用到多个串口的同时在一台PC上使用的情况，例如通过USB转串口等方式来硬件接入串口数目。

那么软件需要判断到底哪些串口号是可用的，才可以初始化相应的串口应用程序。

下面我们简单介绍一下，如何获取PC可用串口端口号，并将其显示在combo box控件中。

例程我们搜寻最多2个可用串口端口。

1. 创建工程，在UI上添加如下控件：
2. 
3. 因为我们需要用到两个串口，所以我们添加两个串口通信插件communications control(如果不需要操作串口，可不用).
4. 添加按键事件处理函数 OnBnClickedStart 
5. 函数处理：

   void CMicrohardTestDlg::OnBnClickedStart()
   {
       // TODO: Add your control notification handler code here
       int i;
       CMscomm1 *pMsc = (CMscomm1*)this->GetDlgItem(IDC_MSCOMM1);
       CComboBox *pcombo = (CComboBox*)this->GetDlgItem(IDC_COMBO1);
       switch (g_w_Steps)
       {
       case 0://check serial port by openning produrce.
       {
                  HANDLE hCom;
                  CString strCOM;;
                  m_Edit1_show = "";
                  pMsc->put_Settings(_T("115200,n,8,1"));
                  pcombo->ResetContent();//clear context
                  for (i = 0; i < 256; i++)
                  {
                      strCOM.Format(_T("COM%d"), i);
                      //open or Create a file or an I/O
                      hCom = CreateFile(_T("\\.\") + strCOM, GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, 0);
                      if (hCom != INVALID_HANDLE_VALUE)
                      {
                          if (m_Edit1_show.IsEmpty())
                          {
                              pcombo->AddString(strCOM);
                              pcombo->SetCurSel(0);
                              pcombo = (CComboBox*)this->GetDlgItem(IDC_COMBO2);
                              m_Edit1_show = "PC Seral Ports Searching ...
   First Port was found.
   ";
                          }
                          else
                          {
                              pcombo->AddString(strCOM);
                              pcombo->SetCurSel(0);
                              m_Edit1_show += "Second Port was found.
   ";
                          }
                      }
                  }
                  if (m_Edit1_show.IsEmpty())
                  {
                      m_Edit1_show = "No PC Serial Port active.";
                  }
                  UpdateData(false);
                  g_w_Steps++;
                 break;
       }
       case 1:
       {
                 break;
       }
       default:
           break;
       }
   }

6. 这里主要函数为

   //open or Create a file or an I/O
    hCom = CreateFile(_T("\\.\") + strCOM, GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, 0);
                      

   返回值不为 INVALID_HANDLE_VALUE 则说明串口端口可用。

7. 到目前为止，我们活跃的串口已经打开了，但是我们并没有设置串口参数。那么我们需要先关有效的端口。更改后为：

   void CMicrohardTestDlg::OnBnClickedStart()
   {
       // TODO: Add your control notification handler code here
       int i,num;
       CString str,num_str;
       CMscomm1 *pMsc;
       CComboBox *pcombo;
       switch (g_w_Steps)
       {
       case 0://check serial port by openning produrce.
       {
                  //point to combo box1
                  pcombo = (CComboBox*)this->GetDlgItem(IDC_COMBO1);
                  //clear context
                  pcombo->ResetContent();
                  num = 0;
                  m_Edit1_show += _T("PC Serial Ports Searching ...
   ");
                  for (i = 0; i < 256; i++)
                  {
                      str.Format(_T("COM%d"), i);
                      //open or Create a file or an I/O
                      HANDLE hCom = CreateFile(_T("\\.\") + str, GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, 0);
                      if (hCom != INVALID_HANDLE_VALUE)
                      {
                          num++;
                          pcombo->AddString(str);
                          pcombo->SetCurSel(0);
                          //point to combo box2
                          pcombo = (CComboBox*)this->GetDlgItem(IDC_COMBO2);
                          m_Edit1_show += str + _T(" was found.
   ");
                      }
                      CloseHandle(hCom);
                      if (num >= 2)break;
                  }
                  if (num >= 2)
                  {
                      SetDlgItemText(IDC_BUTTON1, _T("OpenPorts"));
                      g_w_Steps++;
                  }
                  else
                  {
                      str.Format(_T("%d Port are active, we need at least 2 Port Active.Please re-try.
   "), num);
                      m_Edit1_show += str;
                  }
                  UpdateData(false);
                 break;
       }
       case 1:
       {
                 pMsc = (CMscomm1*)this->GetDlgItem(IDC_MSCOMM1);
                 pcombo = (CComboBox*)this->GetDlgItem(IDC_COMBO1);
                 //open 2 serial port
                 for (i = 0; i < 2; i++)
                 {
                     if (pMsc->get_PortOpen() == TRUE)
                     {
                         pMsc->put_PortOpen(FALSE);
                     }
                     //get combo box text--> str
                     pcombo->GetLBText(0, str);
                     //get str string num-->e.g "COM1235"==> num_str="1235"
                     num_str = str.Mid(3);
                     //get num from string num-->e.g "1235"==>num=1235
                     num = _ttoi(num_str);
                     pMsc->put_CommPort(num);
                     pMsc->put_Settings(_T("115200,n,8,1"));
                     pMsc->put_PortOpen(TRUE);
                     if (pMsc->get_PortOpen() == TRUE)
                     {
                         m_Edit1_show += str + _T(" was Opened Success. Configuration: 115200,n,8,1
   ");
                     }
                     pMsc = (CMscomm1*)this->GetDlgItem(IDC_MSCOMM2);
                     pcombo->EnableWindow(FALSE);
                     pcombo = (CComboBox*)this->GetDlgItem(IDC_COMBO2);
                 }
                 SetDlgItemText(IDC_BUTTON1, _T("Login"));
                 UpdateData(false);
                 g_w_Steps++;
                 break;
       }
       case 2:
       {
                 m_Edit1_show += _T("");
                 break;
       }
       default:
           break;
       }
   }

   这里我们调用 CloseHandle(hCom); 来关闭相应的端口。

谢谢。

End.