winsock IO模型WSAAsynSelect

WSAAsynSelect模型： WSAAsynSelect模型也是一个常用的异步I/O模型。应用程序可以在一个套接字上接收以 WINDOWS消息为基础的网络事件通知。该模型的实现方法是通过调用WSAAsynSelect函 数 自动将套接字设置为非阻塞模式，并向WINDOWS注册一个或多个网络时间，并提供一 个通知时使用的窗口句柄。当注册的事件发生时，对应的窗口将收到一个基于消息的通知。

int  WSAAsyncSelect( SOCKET s, HWND hWnd, u_int wMsg, long lEvent);

s为需要事件通知的套接字 hWnd为接收消息的窗口句柄 wMsg为要接收的消息 lEvent为掩码，指定应用程序感兴趣的网络事件组合，主要如下：

#define FD_READ_BIT 0
#define FD_READ (1 << FD_READ_BIT)
#define FD_WRITE_BIT 1
#define FD_WRITE (1 << FD_WRITE_BIT)
#define FD_OOB_BIT 2
#define FD_OOB (1 << FD_OOB_BIT)
#define FD_ACCEPT_BIT 3
#define FD_ACCEPT (1 << FD_ACCEPT_BIT)

#define FD_CONNECT_BIT 4
#define FD_CONNECT (1 << FD_CONNECT_BIT)
#define FD_CLOSE_BIT 5
#define FD_CLOSE (1 << FD_CLOSE_BIT)

WSAAsynSelect实例：

#include <winsock.h>
#include <tchar.h>

#define PORT         5150
#define MSGSIZE      1024
#define WM_SOCKET     WM_USER+1
#pragma comment(lib, "ws2_32.lib")

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = _T("AsyncSelect Model");
HWND            hwnd ;
MSG             msg ;
WNDCLASS        wndclass ;

wndclass.style            = CS_HREDRAW | CS_VREDRAW ;
wndclass.lpfnWndProc      = WndProc ;
wndclass.cbClsExtra       = 0 ;
wndclass.cbWndExtra       = 0 ;
wndclass.hInstance        = hInstance ;
wndclass.hIcon            = LoadIcon (NULL, IDI_APPLICATION) ;
wndclass.hCursor          = LoadCursor (NULL, IDC_ARROW) ;
wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
wndclass.lpszMenuName     = NULL ;
wndclass.lpszClassName = szAppName ;

if (!RegisterClass(&wndclass))
{
MessageBox (NULL, TEXT ("This program requires Windows NT!"), szAppName, MB_ICONERROR) ;
return 0 ;
}

hwnd = CreateWindow (szAppName,                     // window class name
TEXT ("AsyncSelect Model"), // window caption
WS_OVERLAPPEDWINDOW,           // window style
CW_USEDEFAULT,                 // initial x position
CW_USEDEFAULT,                 // initial y position
CW_USEDEFAULT,                 // initial x size
CW_USEDEFAULT,                 // initial y size
NULL,                          // parent window handle
NULL,                          // window menu handle
hInstance,                     // program instance handle
NULL) ;                        // creation parameters

ShowWindow(hwnd, iCmdShow);
UpdateWindow(hwnd);

while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg) ;
DispatchMessage(&msg) ;
}

return msg.wParam;
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
WSADATA          wsd;
static SOCKET sListen;
SOCKET           sClient;
SOCKADDR_IN      local, client;
int              ret, iAddrSize = sizeof(client);
char             szMessage[MSGSIZE];

switch (message)
{
case WM_CREATE:
// Initialize Windows Socket library
WSAStartup(0x0202, &wsd);

// Create listening socket
sListen = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

// Bind
local.sin_addr.S_un.S_addr = htonl(INADDR_ANY);
local.sin_family = AF_INET;
local.sin_port = htons(PORT);
bind(sListen, (struct sockaddr *)&local, sizeof(local));

// Listen
listen(sListen, 3);

// Associate listening socket with FD_ACCEPT event
WSAAsyncSelect(sListen, hwnd, WM_SOCKET, FD_ACCEPT);
return 0;

case WM_DESTROY:
closesocket(sListen);
WSACleanup();
PostQuitMessage(0);
return 0;

case WM_SOCKET:
if (WSAGETSELECTERROR(lParam))//lParam的高字节包含了可能出现的任何的错误代码
{
closesocket(wParam);
break;
}

switch (WSAGETSELECTEVENT(lParam)) //lParam的低字节指定已经发生的网络事件
{
case FD_ACCEPT:
// Accept a connection from client
sClient = accept(wParam, (struct sockaddr *)&client, &iAddrSize);

// Associate client socket with FD_READ and FD_CLOSE event
WSAAsyncSelect(sClient, hwnd, WM_SOCKET, FD_READ | FD_CLOSE);
break;

case FD_READ:
ret = recv(wParam, szMessage, MSGSIZE, 0);

if (ret == 0 || ret == SOCKET_ERROR && WSAGetLastError() == WSAECONNRESET)
{
closesocket(wParam);
}
else
{
szMessage[ret] = '\0';
send(wParam, szMessage, strlen(szMessage), 0);
}
break;

case FD_CLOSE:
closesocket(wParam);
break;
}
return 0;
}

return DefWindowProc(hwnd, message, wParam, lParam);
}

当应用程序窗口hWnd收到消息时，wMsg.wParam参数标识了套接字，lParam的低字标明 了网络事件，高字则包含错误代码。