异步套接字示例

#include <winsock2.h>

#define UM_READ_DATA (WM_USER + 1)
#define BUFFERSIZE 512
#define PORT_NUMBER 10000

SOCKET g_udpSocket;

BOOL InitSocket(HWND hWnd)
{
  WSADATA wsaData;
  WSAStartup(MAKEWORD(2, 0), &wsaData);
  g_udpSocket = WSASocket(AF_INET, SOCK_DGRAM, 0, NULL, NULL, 0);

  SOCKADDR_IN addrIn;
  addrIn.sin_addr.S_un.S_addr = htonl(INADDR_ANY);
  addrIn.sin_family = AF_INET;
  addrIn.sin_port = htons(PORT_NUMBER);

  bind(g_udpSocket, (SOCKADDR*) &addrIn, sizeof(SOCKADDR));

  WSAAsyncSelect(g_udpSocket, hWnd, UM_READ_DATA, FD_READ);

  return TRUE;
}

LRESULT OnReadData(WPARAM wParam, LPARAM lParam)
{
  if (FD_READ == LOWORD(lParam))
    {
      CHAR* szBuffer = new CHAR[BUFFERSIZE];
      WSABUF wsabuf;
      wsabuf.buf = szBuffer;
      wsabuf.len = BUFFERSIZE;

      DWORD dwRecv;
      DWORD dwFlag;
      SOCKADDR_IN addrIn;
      int nLen = sizeof(SOCKADDR);

      WSARecvFrom(g_udpSocket, &wsabuf, 1, &dwRecv, &dwFlag, (SOCKADDR*) &addrIn,
                  &nLen, NULL, NULL);

      UINT cbWstr = MultiByteToWideChar(CP_ACP, 0, wsabuf.buf, -1, NULL, 0);
      WCHAR* szWstr = new WCHAR[cbWstr];
      MultiByteToWideChar(CP_ACP, 0, wsabuf.buf, -1, szWstr, cbWstr);
      delete szWstr;
    }
  return 0;
}

void OnSendData(DWORD dwHost, LPCWSTR lpszSend)
{
  SOCKADDR_IN addrIn;
  addrIn.sin_addr.S_un.S_addr = htonl(dwHost);
  addrIn.sin_family = AF_INET;
  addrIn.sin_port = htons(PORT_NUMBER);

  UINT cbStr = WideCharToMultiByte(CP_ACP, 0, lpszSend, -1, NULL, 0, NULL, NULL);
  CHAR* szStr = new CHAR[cbStr];
  WideCharToMultiByte(CP_ACP, 0, lpszSend, -1, szStr, cbStr, NULL, NULL);

  WSABUF wsabuf;
  wsabuf.buf = szStr;
  wsabuf.len = cbStr;

  DWORD dwSend;
  int nLen = sizeof(SOCKADDR);
  WSASendTo(g_udpSocket, &wsabuf, 1, &dwSend, 0, (SOCKADDR*) &addrIn, nLen, NULL, NULL);
}