请教：VC编程检测设备是否连接？

Question

VC编程怎样检测设备是否已连接？

Answer 1

How about handshaking ??

Answer 2

//HOWTO: Enumerate Hardware Devices by Using SetupDi Calls Q259695#include <stdio.h>
#include <windows.h>
#include <setupapi.h>
#include <devguid.h>
#include <regstr.h>
#pragma comment(lib,"Setupapi.lib")
void printdata(LPVOID pdata,DWORD datalen,DWORD type);int main( int argc, char *argv[ ], char *envp[ ] )
{
    HDEVINFO hDevInfo;
    SP_DEVINFO_DATA DeviceInfoData;
    DWORD i;    // Create a HDEVINFO with all present devices.
    hDevInfo = SetupDiGetClassDevs(NULL,
        0, // Enumerator
        0,
        DIGCF_PRESENT | DIGCF_ALLCLASSES );
    
    if (hDevInfo == INVALID_HANDLE_VALUE)
    {
        // Insert error handling here.
        return 1;
    }
    
    // Enumerate through all devices in Set.
    
    DeviceInfoData.cbSize = sizeof(SP_DEVINFO_DATA);
    for (i=0;SetupDiEnumDeviceInfo(hDevInfo,i,
        &DeviceInfoData);i++)
    {
        DWORD DataT;
        LPTSTR buffer = NULL;
        DWORD buffersize = 0;
        
        // 
        // Call function with null to begin with, 
        // then use the returned buffer size 
        // to Alloc the buffer. Keep calling until
        // success or an unknown failure.
        // 
        while (!SetupDiGetDeviceRegistryProperty(
            hDevInfo,
            &DeviceInfoData,
            SPDRP_DEVICEDESC,
            &DataT,
            (PBYTE)buffer,
            buffersize,
            &buffersize))
        {
            if (GetLastError() == 
                ERROR_INSUFFICIENT_BUFFER)
            {
                // Change the buffer size.
                if (buffer) LocalFree(buffer);
                buffer = (char*)LocalAlloc(LPTR,buffersize);
            }
            else
            {
                // Insert error handling here.
                break;
            }
        }        
        printf("SPDRP_DEVICEDESC:[%s]\n",buffer);
if (buffer) LocalFree(buffer); buffer =NULL;
buffersize=0;
        while (!SetupDiGetDeviceRegistryProperty(
            hDevInfo,
            &DeviceInfoData,
            SPDRP_LOCATION_INFORMATION,
            &DataT,
            (PBYTE)buffer,
            buffersize,
            &buffersize))
        {
            if (GetLastError() == 
                ERROR_INSUFFICIENT_BUFFER)
            {
                // Change the buffer size.
                if (buffer) LocalFree(buffer);
                buffer = (char*)LocalAlloc(LPTR,buffersize);
            }
            else
            {
                // Insert error handling here.
                break;
            }
        }        
        printf("SPDRP_LOCATION_INFORMATION:[%s]\n",buffer);        
        if (buffer) LocalFree(buffer); buffer =NULL;
buffersize=0;
        while (!SetupDiGetDeviceRegistryProperty(
            hDevInfo,
            &DeviceInfoData,
            SPDRP_ADDRESS,
            &DataT,
            (PBYTE)buffer,
            buffersize,
            &buffersize))
        {
            if (GetLastError() == 
                ERROR_INSUFFICIENT_BUFFER)
            {
                // Change the buffer size.
                if (buffer) LocalFree(buffer);
                buffer = (char*)LocalAlloc(LPTR,buffersize);
            }
            else
            {
                // Insert error handling here.
                break;
            }
        }        
printf("Length:%d,SPDRP_ADDRESS:",buffersize);   
printdata(buffer,buffersize,DataT);
printf("\n");
        if (buffer) LocalFree(buffer);    }
    
    
    if ( GetLastError()!=NO_ERROR &&
         GetLastError()!=ERROR_NO_MORE_ITEMS )
    {
        // Insert error handling here.
        return 1;
    }
    
    //  Cleanup
    SetupDiDestroyDeviceInfoList(hDevInfo);
    
    return 0;
} void printdata(LPVOID pdata,DWORD datalen,DWORD type)
{
if(datalen<=0)
return;
switch(type)
{
case REG_DWORD:
{
PDWORD np=(PDWORD)pdata;
printf("REG_DWORD:%d",np[0]);
}
break;
case REG_SZ:
printf("REG_SZ:%d",(LPCTSTR)pdata);
break;
default:
printf("other format");
break;
}
}
//HOWTO: Force Reenumeration of a Device Tree From an Application Q259697