完成端口服务器模型

前提:

IOCP的整体编程模型跟上面的纯重叠io 非常类似.  纯重叠io使用OVERLAPPED  + APC函数完成.

这种模型的缺点是必须让调用apc函数进入alterable状态. 而IOCP解决了这个问题.IOCP让我们自己创建一些线程,

然后调用GetQueuedCompletionStatus 来告诉我们某个io操作完成, 就像是在另一个线程中执行了APC函数一样;

使用IOCP 的时候,一般情况下需要自己创建额外的线程,用于等待结果完成(GetQueuedCompletionStatus)

使用到的函数:

CreateIoCompletionPort : 创建/ 关联一个完成端口 .

第3个参数是一个自定义数据, 第4个是最多N个线程可被调用;

注意与其关联的HANDLE 必须要有OVERLAPPED属性的

//创建一个完成端口
HANDLE hComp = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 0)
 
 
//关联到完成端口. 第3个参数是一个自定义数据
//在GetQueuedCompletionStatus将携带这些数据返回. 这个自定义数据将一直与此套接字绑定在了一起
CreateIoCompletionPort((HANDLE)client_socket, hComp, (DWORD)pSockData, 0);

GetQueuedCompletionStatus ：一旦类似WSARecv / WSASend 完成后 . 用此函数获取结果,就想APC函数一样,一旦完成io操作就调用. 此函数一般情况都在某一个线程中使用.注意一旦在某个线程中调用了此函数,这意味着,

该线程就像被指派给了IOCP一样,供IOCP使用. 总之这个行为就想APC函数在另一个线程被调用了;

关于解除关联: 一旦一个套接字关闭了 , closehandle /closesocket. 就将从IOCP的设备句柄列表中解除关联了

关于线程:

CreateIoCompletionPort  最后一个参数用于指定IOCP最多执行N个线程(如果是0 则使用默认CPU的核数). 但一般情况下,我会预留一些额外的线程.比如

我的CPU是4核即IOCP最多可使用 4个线程 , 不过一般情况下会创建 8 个线程,给IOCP预留 额外4个线程 . 原因是如果IOCP

有5个任务已经完成, 最多只有4个线程被唤醒. 如果其中某个线程调用了WaitForSingleObject 之类的函数 ,此时IOCP将唤醒额外的线程来处理第5个任务;

先补充一下. 对于WSARecv / WSASend 的OVERLAPPED操作,简称为投递操作.意思是让操作系统去干活,至于什么时候干完.

GetQueuedCompletionStatus 会通知你(即返回) . 因此因此, 需要注意, 这些参数像WSABUF 和 OVERLAPPED 一定要 new / malloc在堆中;

代码中都有注释: 另代码中有很多返回都没判断.这个例子仅仅解释如何编写IOCP

#include "stdafx.h"
#include <process.h>
#include "../utils.h" //包含了一些宏和一些打印错误信息的函数. 
 
#define BUFFSIZE 8192
#define Read 0
#define Write 1
 
//自定义数据 .  注意 结构的地址 与 第一个成员的地址相同
struct IOData
{
    WSAOVERLAPPED overlapped;  //每个io操作都需要独立的一个overlapped
    WSABUF wsabuf;   //读写各一份
    int rw_mode;         //判断读写操作
    char * buf;              //真正存放数据的地方, 需要初始化
};
 
//自定义数据.保存客户套接字和地址
struct SocketData
{
    SOCKET hClientSocket;        //客户端套接字
    SOCKADDR_IN clientAddr;
    IOData * pRead;                    //2个指针,只是为了在线程中方便使用添加的
    IOData * pWrite;
};
 
 
//用于交换2个buf
int swapBuf(WSABUF * a, WSABUF * b)
{
    BOOL ret = FALSE;
    if (a && b){
        char * buf = a->buf;
        a->buf = b->buf;
        b->buf = buf;
        ret = TRUE;
    }
    return ret;
}
 
//释放内存,解除关联
void freeMem(SocketData * pSockData)
{
    closesocket(pSockData->hClientSocket);
    free(pSockData->pRead->buf);
    free(pSockData->pWrite->buf);
    free(pSockData->pWrite);
    free(pSockData->pRead);
    free(pSockData);
}
 
 
unsigned int WINAPI completeRoutine(void * param)
{
    //完成端口
    HANDLE hCom = (HANDLE)param;
 
    SocketData * pSockData = NULL;
    IOData * pIOData = NULL;
    DWORD flags = 0, bytes = 0; 
    BOOL ret = 0;
    SOCKET hClientSocket = NULL;
    printf("tid:%ld start!\n", GetCurrentThreadId());
 
    while (1)
    {
        flags = 0;
        
        //直到有任务完成即返回
        ret = GetQueuedCompletionStatus(hCom, &bytes,
            (PULONG_PTR)&pSockData,
            (LPOVERLAPPED * )&pIOData,
            INFINITE);
        printf("GetQueuedCompletionStatus : %d , diy key : %p , pIOData:%p,mode:%d\n", ret, pSockData,
            pIOData,pIOData->rw_mode);
 
        //如果成功了
        if (ret)
        {
            hClientSocket = pSockData->hClientSocket;
 
            //如果是WSARecv的
            if (Read == pIOData->rw_mode)
            {
                printf("READ - > bytesRecved:%ld, high:%ld\n", bytes, pIOData->overlapped.InternalHigh);
 
                //对端关闭
                if (0 == bytes)
                {
                    printf("peer closed\n");
                    freeMem(pSockData);  //释放内存
                    continue;
                } 
 
                //测试数据 
                pSockData->pRead->buf[bytes] = 0;
                printf("Read buf:%s\n", pSockData->pRead->buf);
 
                //交换指针, 把recv的buf 给 write的buf;
                //把write的buf交换给recv . 如果并发量不大的时候可以这么做
                swapBuf(&pIOData->wsabuf, &pSockData->pWrite->wsabuf);
 
                //回传操作.清空write OVERLAPPED
                memset(&pSockData->pWrite->overlapped, 0, sizeof(WSAOVERLAPPED));
                pSockData->pWrite->wsabuf.len = bytes;
                WSASend(hClientSocket, &pSockData->pWrite->wsabuf,
                    1, NULL, 0, &pSockData->pWrite->overlapped, NULL);
 
                //再次投递一个recv操作,等待下次客户端发送
                memset(&pSockData->pRead->overlapped, 0, sizeof(WSAOVERLAPPED));
                pSockData->pRead->wsabuf.len = BUFFSIZE;
                WSARecv(hClientSocket, &pSockData->pRead->wsabuf, 1, NULL, &flags,
                    &pSockData->pRead->overlapped, NULL);
            }
            else {
 
                 // send 完成.
                printf("Send finsished - > bytes:%ld, high:%ld\n", bytes, pIOData->overlapped.InternalHigh);
                memset(&pIOData->overlapped, 0, sizeof(WSAOVERLAPPED));
            }
        }
        else{
            //一旦出错, 解除绑定即删除内存
            print_error(GetLastError());
            freeMem(pSockData);
        }
    }
 
    return 0;
}
int _tmain(int argc, _TCHAR* argv[])
{
    WSADATA wsadata;
    if (WSAStartup(MAKEWORD(2, 2), &wsadata) != 0){
        print_error(WSAGetLastError());
        return 0;
    }
    SYSTEM_INFO sysinfo;
    GetSystemInfo(&sysinfo);
 
    //指定线程数量. 一般 processors * 2
    const DWORD nThreads = sysinfo.dwNumberOfProcessors * 2;
 
    //创建一个完成端口 ,  前3个参数保证了创建一个独立的完成端口, 最后一个参数指定了完成
    //端口可使用的线程数. 0 使用当前cpu核数
    HANDLE hCom = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 0);
 
    //准备一些线程供完成端口调用, 把完成端口同时传入
    HANDLE  * arr_threads = new HANDLE[nThreads];
    for (int i = 0; i < sysinfo.dwNumberOfProcessors; ++i)
        arr_threads[i] = (HANDLE)_beginthreadex(NULL, 0, completeRoutine, (void*)hCom, 0, NULL);
 
 
    //创建一个支持OVERLAPPED的socket.这样的属性将被 accept 返回的socket所继承
    SOCKET hListenSocket = WSASocket(AF_INET, SOCK_STREAM, 0, NULL, 0, WSA_FLAG_OVERLAPPED);
    SOCKADDR_IN serv_addr, client_addr;
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(PORT);
    serv_addr.sin_addr.s_addr = INADDR_ANY;
 
    bind(hListenSocket, (SOCKADDR*)&serv_addr, sizeof(serv_addr));
    listen(hListenSocket, BACKLOG);
 
    SOCKET client_socket;
    int client_addr_size = 0;
    DWORD flags = 0;
    while (1){
        client_addr_size = sizeof(client_addr);
        flags = 0;
        client_socket = accept(hListenSocket, (SOCKADDR*)&client_addr, &client_addr_size);
        puts("accepted");
 
        //准备一份数据, 用于保存clientsocket, addr, 以及读写指针;
        SocketData * pSockData = (SocketData *)malloc(sizeof(SocketData));
        pSockData->pRead = NULL;
        pSockData->pWrite = NULL;
        pSockData->hClientSocket = client_socket;
        memcpy(&pSockData->clientAddr, &client_addr, client_addr_size);
 
        
        //准备数据
        IOData *  pRead = (IOData *)malloc(sizeof(IOData));
        //对于OVERLAPPED,需要额外注意,清0
        memset(&pRead->overlapped, 0, sizeof(WSAOVERLAPPED));
        pRead->buf = (char *)malloc(BUFFSIZE);
        pRead->rw_mode = Read;
        pRead->wsabuf.buf = pRead->buf;
        pRead->wsabuf.len = BUFFSIZE;
        pSockData->pRead = pRead;
 
        IOData *pWrite = (IOData *)malloc(sizeof(IOData));
        pWrite->buf = (char *)malloc(BUFFSIZE);
        memset(&pWrite->overlapped, 0, sizeof(WSAOVERLAPPED));
        pWrite->rw_mode = Write;
        pWrite->wsabuf.buf = pWrite->buf;
        pWrite->wsabuf.len = BUFFSIZE;
        pSockData->pWrite = pWrite;
 
 
        //与iocp关联在一起. 注意第3个参数, 把自定义数据一起传递过去
        CreateIoCompletionPort((HANDLE)client_socket, hCom, (DWORD)pSockData, 0);
        WSARecv(client_socket, &pRead->wsabuf, 1, NULL, &flags, &pRead->overlapped, NULL);
    }
 
    return 0;
}