Socket I/O模型之异步选择(WSAAsyncSelect)

http://tangfeng.iteye.com/blog/518141

用异步选择模型，应用程序可在一个套接字上，接收以Windows消息为基础的网络事件通知。具体的做法是在建好一个套接字后，调用WSAAsyncSelect函数。 

服务器端代码： 

// write by larry
// 2009-8-20
// This is a server using WSAAsyncSelect model.
#include "stdafx.h"
#include <winsock.h>
#include <tchar.h>
#define PORT  5150
#define MSGSIZE  1024
#define WM_SOCKET  WM_USER+0
#pragma comment(lib, "ws2_32.lib")
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    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, _T("This program requires Windows NT!"), szAppName, MB_ICONERROR);
        return 0;
    }
    hwnd = CreateWindow(szAppName, // window class name
        _T("AsyncSelect Model"),   // window caption
        WS_OVERLAPPEDWINDOW,       // window stype
        CW_USEDEFAULT,             // initial x postion
        CW_USEDEFAULT,             // initial y postion
        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, nCmdShow);
    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 wsaData;
    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, &wsaData);
        // Create listening socket
        sListen = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
        // Bind
        local.sin_family = AF_INET;
        local.sin_addr.S_un.S_addr = htonl(INADDR_ANY);
        local.sin_port = htons(PORT);
        bind(sListen, (sockaddr*)&local, sizeof(SOCKADDR_IN));
        // 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))
        {
            closesocket(wParam);
            break;
        }
        switch (WSAGETSELECTEVENT(lParam))
        {
        case FD_ACCEPT:
            // Accept a connection from client
            sClient = accept(wParam, (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);
}

服务器端得主要流程： 
1.在WM_CREATE消息处理函数中，初始化Windows Socket library，创建监听套接字，绑定，监听，并且调用WSAAsyncSelect函数表示我们关心在监听套接字上发生的FD_ACCEPT事件； 
2.自定义一个消息WM_SOCKET，一旦在我们所关心的套接字（监听套接字和客户端套接字）上发生了某个事件，系统就会调用WndProc并且message参数被设置为WM_SOCKET； 
3.在WM_SOCKET的消息处理函数中，分别对FD_ACCEPT、FD_READ和FD_CLOSE事件进行处理； 
4.在窗口销毁消息(WM_DESTROY)的处理函数中，我们关闭监听套接字，清除Windows Socket library 

WSAAsyncSelect函数的网络事件类型可以有以下一种： 
FD_READ 应用程序想要接收有关是否可读的通知，以便读入数据 
FD_WRITE 应用程序想要接收有关是否可写的通知，以便写入数据 
FD_OOB 应用程序想接收是否有带外（OOB）数据抵达的通知 
FD_ACCEPT 应用程序想接收与进入连接有关的通知 
FD_CONNECT 应用程序想接收与一次连接或者多点join操作完成的通知 
FD_CLOSE 应用程序想接收与套接字关闭有关的通知 
FD_QOS 应用程序想接收套接字“服务质量”（QoS）发生更改的通知 
FD_GROUP_QOS  应用程序想接收套接字组“服务质量”发生更改的通知（现在没什么用处，为未来套接字组的使用保留） 
FD_ROUTING_INTERFACE_CHANGE 应用程序想接收在指定的方向上，与路由接口发生变化的通知 
FD_ADDRESS_LIST_CHANGE  应用程序想接收针对套接字的协议家族，本地地址列表发生变化的通知