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8.2.2 WSAAsyncSelect
接收以windows消息为基础的网络事件通知。
int WSAAsyncSelect(SOCKET s, HWND hWnd, unsigned int wMsg, long lEvent);
FD_READ, FD_WRITE, FD_ACCEPT, FD_CONNECT和FD_CLOSE.
从锁定变成非锁定状态。
#define WM_SOCKET WM_USER+1
#define

int WINAPI WinMain(IN HINSTANCE hInstance, IN HINSTANCE hPrevInstance, IN LPSTR lpCmdLine, IN int nShowCmd )
{
SOCKET Listen;
HWND Window;
sockaddr InternetAddr;

Window = CreateWindow();

WSAStartup(...);

Listen = socket(...);

InternetAddr.sin_family = AF_INET;
InternetAddr.sin_addr.s_addr = htonl(INADDR_ANY);
InternetAddr.sin_port = htons(5150);

bind(Listen, (PSOCKADDR)&InternetAddr,sizeof(InternetAddr));

WSAAsyncSelect(Listen, Window, WM_SOCKET, FD_ACCEPT|FD_CLOSE);

listen(Listen, 5);

//Translate and dispatch window messages until the application terminates
}

BOOL CALLBACK ServerWinProc(HWND hDlg, WORD wMsg,WORD wParam, DWORD lParam)
{
SOCKET Accept;
switch(wMsg)
{
case WM_PAINT:
break;
case WM_SOCKET:

//Determine whether an error occurred on the socket by using the WSAGETSLECTERRROR() macro
if (WSAGETSELECTERROR(lParam))
{
closesocket(wParam);
break;
}

//Determine what event occurred on the socket
switch(WSAGETSELECTEVENT(lParam))
{
case FD_ACCEPT:
Accept = accept(wParam, NULL, NULL);

//Prepare accepted socket for read, write and close notification.
WSAAsyncSelect(Accept, hwnd, WM_SOCKET, FD_READ|FD_WRITE|FD_CLOSE);
break;
case FD_READ:
//Receive data from the socket in wparam;
break;
case FD_WRITE:
//The socket in param is ready for sending data;
break;
case FD_CLOSE:
//The connection is now closed
closesocket(wParam);
break;
}
break;
}
return true;
}
产生FD_WRITE通知的三种条件
1.使用connect或者WASConnect,一个套接字首次建立了连接。
2.使用accept or WSAAccept,套接字被接受以后。
3.若send WSASend,sendto WSASendto操作失败，返回了WSAEWOULDBLOCK错误，而且缓冲区的空间变得可用。