轉自http://www.cnblogs.com/pen-ink/articles/1834088.html


HANDLE WINAPI CreateIoCompletionPort(
  __in          HANDLE FileHandle,
  __in          HANDLE ExistingCompletionPort,
  __in          ULONG_PTR CompletionKey,
  __in          DWORD NumberOfConcurrentThreads
);
/*
這個函數完成兩個不同的任務：1、創建一個完成端口對象；2、將一個或者多個文件句柄關聯到I/O完成端口對象?？煞殖蓛蓚€小函數對CreateIoCompletionPort調用進行抽象。
*/
//1、創建I/O完成端口
HANDLE CreateNewCompletionPort(DWORD dwNumberOfConcurrentThreads)
{
    return (CreateNewCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, dwNumberOfConcurrentThreads));
}
//2、將設備與I/O完成端口關聯起來
BOOL AssociateDeviceWithCompletionPort(HANDLE hCompletionPort, HANDLE hDevice, DWORD dwCompletionKey)
{
    HANDLE h = CreateIoCompletionPort(hDevice, hCompletionPort, dwCompletionKey, 0);
    return (h == hCompletionPort);
}

/////////////////////////////////////////////////
// IOCPDemo.cpp文件            調試通過

#include "WSAInit.h"
#include <stdio.h>
#include <windows.h>

// 初始化Winsock庫
CWSAInit theSock;

#define BUFFER_SIZE 1024
#define OP_READ   1
#define OP_WRITE  2
#define OP_ACCEPT 3

typedef struct _PER_HANDLE_DATA        // per-handle數據
{
    SOCKET s;            // 對應的套節字句柄
    sockaddr_in addr;    // 客戶方地址
    char buf[BUFFER_SIZE];    // 數據緩沖區
    int nOperationType;        // 操作類型
} PER_HANDLE_DATA, *PPER_HANDLE_DATA;

DWORD WINAPI ServerThread(LPVOID lpParam)
{
    // 得到完成端口對象句柄
    HANDLE hCompletion = (HANDLE)lpParam;

    DWORD dwTrans;
    PPER_HANDLE_DATA pPerHandle;
    OVERLAPPED *pOverlapped;
    while(TRUE)
    {
        // 在關聯到此完成端口的所有套節字上等待I/O完成
        BOOL bOK = ::GetQueuedCompletionStatus(hCompletion, 
            &dwTrans, (PULONG_PTR)&pPerHandle, &pOverlapped, WSA_INFINITE);
        if(!bOK)                        // 在此套節字上有錯誤發生
        {
            ::closesocket(pPerHandle->s);
            ::GlobalFree(pPerHandle);
            ::GlobalFree(pOverlapped);
            continue;
        }

        if(dwTrans == 0 &&                // 套節字被對方關閉
            (pPerHandle->nOperationType == OP_READ || pPerHandle->nOperationType == OP_WRITE))    

        {
            ::closesocket(pPerHandle->s);
            ::GlobalFree(pPerHandle);
            ::GlobalFree(pOverlapped);
            continue;
        }

        switch(pPerHandle->nOperationType)    // 通過per-I/O數據中的nOperationType域查看什么I/O請求完成了
        {
        case OP_READ:    // 完成一個接收請求
            {
                pPerHandle->buf[dwTrans] = '\0';
                printf(pPerHandle-> buf);

                // 繼續投遞接收I/O請求
                WSABUF buf;
                buf.buf = pPerHandle->buf ;
                buf.len = BUFFER_SIZE;
                pPerHandle->nOperationType = OP_READ;
    
                DWORD nFlags = 0;
                ::WSARecv(pPerHandle->s, &buf, 1, &dwTrans, &nFlags, pOverlapped, NULL);
            }
            break;
        case OP_WRITE: // 本例中沒有投遞這些類型的I/O請求
        case OP_ACCEPT:
            break;
        }
    }
    return 0;
}


void main()
{
    int nPort = 4567;
    // 創建完成端口對象，創建工作線程處理完成端口對象中事件
    HANDLE hCompletion = ::CreateIoCompletionPort(INVALID_HANDLE_VALUE, 0, 0, 0);
    ::CreateThread(NULL, 0, ServerThread, (LPVOID)hCompletion, 0, 0);

    // 創建監聽套節字，綁定到本地地址，開始監聽
    SOCKET sListen = ::socket(AF_INET, SOCK_STREAM, 0);
    SOCKADDR_IN si;
    si.sin_family = AF_INET;
    si.sin_port = ::ntohs(nPort);
    si.sin_addr.S_un.S_addr = INADDR_ANY;
    ::bind(sListen, (sockaddr*)&si, sizeof(si));
    ::listen(sListen, 5);

    // 循環處理到來的連接
    while(TRUE)
    {
        // 等待接受未決的連接請求
        SOCKADDR_IN saRemote;
        int nRemoteLen = sizeof(saRemote);
        SOCKET sNew = ::accept(sListen, (sockaddr*)&saRemote, &nRemoteLen);
        // 接受到新連接之后，為它創建一個per-handle數據，并將它們關聯到完成端口對象。
        PPER_HANDLE_DATA pPerHandle = 
            (PPER_HANDLE_DATA)::GlobalAlloc(GPTR, sizeof(PER_HANDLE_DATA));
        pPerHandle->s = sNew;
        memcpy(&pPerHandle->addr, &saRemote, nRemoteLen);
        pPerHandle->nOperationType = OP_READ;
        ::CreateIoCompletionPort((HANDLE)pPerHandle->s, hCompletion, (ULONG_PTR)pPerHandle, 0);
        // 投遞一個接收請求
        OVERLAPPED *pol = (OVERLAPPED *)::GlobalAlloc(GPTR, sizeof(OVERLAPPED));
        WSABUF buf;
        buf.buf = pPerHandle->buf;
        buf.len = BUFFER_SIZE;    
        DWORD dwRecv;
        DWORD dwFlags = 0;
        ::WSARecv(pPerHandle->s, &buf, 1, &dwRecv, &dwFlags, pol, NULL);
    }
}