基于重叠IO模型的 回显TCP服务器设计

---------------------1 套接字对象----------------------

为每个套接字创建一个SOCKET_OBJ对象，记录与之相关的信息。

 typedef struct _SOCKET_OBJ{
    SOCKET s;
    int nOutstandingOps;//重叠IO数量
    LPFN_ACCEPTEX lpfnAcceptEx; //扩展AcceptEx指针
}SOCKET_OBJ,*PSOCKET_OBJ;

所有重叠IO提交到特定的套接字上，释放对应套接字对象，必须保证此套接字再没有重叠IO，即nOutstandingOps=0

申请套接字对象，释放套接字对象的函数

 PSOCKET_OBJ GetSocketObj(SOCKET s){
     PSOCKET_OBJ pSocket = (PSOCKET_OBJ)::GlobalAlloc(GPTR,sizeof(SOCKET_OBJ));
     if(pSocket != NULL)
         pSocket->s = s;
     return pSocket;
 }
 void FreeSocketObj(PSOCKET_OBJ pSocket){
     if(pSocket->s != INVALID_SOCKET)
         ::closesocket(pSocket->s);
     ::GlobalFree(pSocket);
 }

---------------------2 缓冲区对象---------------------

缓冲区对象SOCKET_OBJ，记录重叠IO的所有属性

 typedef struct _BUFFER_OBJ{
    OVERLAPPED ol;//重叠结构
    char *buff;//使用的缓冲区
    int nLen;//buff长度
    PSOCKET_OBJ pSocket;//次io所属的套接字对象
    int nOperation;//提交的操作类型
#define OP_ACCEPT    1
#define OP_READ        2
#define OP_WRITE    3
    SOCKET sAccept;//保存AcceptEx接受客户套接字
    _BUFFER_OBJ *pNext;
 }BUFFER_OBJ,*PBUFFER_OBJ;

pNext将BUFFER_OBJ对象练成一个链表

事件句柄数组 和 链表地址

HANDLE g_events[WSA_MAXIMUM_WAIT_EVENTS];
int g_nBufferCount;//数量
PBUFFER_OBJ g_pBufferHead,g_pBufferTail;//地址

调用重叠IO函数之前，都要申请BUFFER_OBJ对象，记录信息。IO完成后，再释放BUFFER_OBJ对象

申请BUFFER_OBJ对象 的函数：

PBUFFER_OBJ GetBufferObj(PSOCKET_OBJ pSocket,ULONG nLen){
    if(g_nBufferCount > WSA_MAXIMUM_WAIT_EVENTS)
        return NULL;
    PBUFFER_OBJ pBuffer = (PBUFFER_OBJ)::GlobalAlloc(GPTR,sizeof(BUFFER_OBJ));
    if(pBuffer!=NULL)
    {
        pBuffer->buff = (char*)::GlobalAlloc(GPTR,nLen);
        pBuffer->ol.hEvent = ::WSACreateEvent();
        pBuffer->pSocket = pSocket;
        pBuffer->sAccept = INVALID_SOCKET;

        //将新的BUFFER_OBJ添加到列表
        if(g_pBufferHead == NULL)
        {
            g_pBufferHead = g_pBufferTail = pBuffer;
        }
        else
        {
            g_pBufferTail->pNext = pBuffer;
            g_pBufferTail = pBuffer;
        }
        g_events[++g_nBufferCount] = pBuffer->ol.hEvent;
    }
    return pBuffer;
}

释放BUFFER_OBJ对象函数：

void FreeBufferObj(PBUFFER_OBJ pBuffer){
    //从列表中移除BUFFER_OBJ对象
    PBUFFER_OBJ pTest = g_pBufferHead;
    BOOL bFind = FALSE;
    if(pTest == pBuffer){
        g_pBufferHead = g_pBufferTail = NULL;
        bFind = TRUE;
    }
    else{
        while(pTest!=NULL && pTest->pNext!=pBuffer)
            pTest = pTest->pNext;
        if(pTest!=NULL){
            pTest->pNext = pBuffer->pNext;
            if(pTest->pNext == NULL)
                g_pBuffer Tail = pTest;
            bFind = TRUE;
        }
    }
    //释放它占用的空间
    if(bFind)
    {
        g_pBufferCount--;
        ::CloseHandle(pBuffer->ol.hEvent);
        ::GlobalFree(pBuffer->buff);
        ::GlobalFree(pBuffer);
    }
}

提交重叠IO，传递参数有重叠结构IO和缓冲区指针buff。在IO完成后，得到的是受信事件对象的句柄。根据这个句柄找到对应的BUFFER_OBJ对象。

查找BUFFER_OBJ对象的代码：

PBUFFER_OBJ FindBufferObj(HANDLE hEvent){
    PBUFFER_OBJ pBuffer = g_pBufferHead;
    while(pBuffer != NULL){
        if(pBuffer->ol.hEvent == hEvent)
            break;
        pBuffer = pBuffer->pNext;
    }
    return pBuffer;
}

更新时间句柄数组g_events中的内容：

void RebuildArray(){
    PBUFFER_OBJ pBuffer = g_pBufferHead;
    int i= 1;
    while(pBuffer != NULL){
        g_events[i++] = pBuffer->ol.hEvent;
        pBuffer = pBuffer->pNext;
    }
}

---------------------3 提交重叠IO---------------------

投递IO之后，线程在重叠IO事件上等待，一旦IO事件对象受信，等待函数就会返回

提交接受连接的BUFFER_OBJ对象代码：

BOOL PostAccept(PBUFFER_OBJ pBuffer){
    PSOCKET_OBJ pSocket = pBuffer->pSocket;
    if(pSocket->lpfnAcceptEx != NULL){
        //设置IO类型，增加套接字上的重叠IO计数
        pBuffer->nOperation = OP_ACCEPT;
        pSocket->nOutstandingOps++;
        //投递此重叠IO
        DWORD dwBytes;
        pBuffer->sAccept = ::WSASocket(AF_INET,SOCK_STREAM,0,NULL,0,WSA_FLAG_OVERLAPPED);
        BOOL b = pSocket->lpfnAcceptEx(
            pSocket->s,
            pBuffer->sAccept,
            pBuffer->buff,
            BUFFER_SIZE - ((sizeof(sockaddr_in+16))*2),
            sizeof(sockaddr_in)+16,
            sizeof(sockaddr_in)+16,
            &dwBytes,
            &pBuffer->ol
            );
        if(!b){
            if(::WSAGetLastError()!=WSA_IO_PENDING)
                return FALSE;
        }
        return TRUE;
    }
    return FALSE;
};

接收数据的BUFFER_OBJ对象代码：

BOOL PostRecv(PBUFFER_OBJ pBuffer){
    //设置IO类型，增加套接字上的重叠IO计数
    pBuffer->nOperation = OP_ACCEPT;
    pBuffer->pSocket->nOutstandingOps++;
    //投递此重叠IO
    DWORD dwBytes;
    DWORD dwFlags = 0;
    WSABUF buf;
    buf.buf = pBuffer->buff;
    buf.len = pBuffer->nLen;
    if(::WSARecv(pBuffer->pSocket->s,&buf,1,&dwBytes,&dwFlags,&pBuffer->ol,NULL)!=NO_ERROR){
        if(::WSAGetLastError()!= WSA_IO_PENDING)
            return FALSE;
    }
    return TRUE;
}

发送数据额BUFFER-obj对象代码：

BOOL PostSend(PBUFFER_OBJ pBuffer){
    //设置IO类型，增加套接字上的重叠IO计数
    pBuffer->nOperation = OP_ACCEPT;
    pBuffer->pSocket->nOutstandingOps++;
    //投递此重叠IO
    DWORD dwBytes;
    DWORD dwFlags;
    WSABUF buf;
    buf.buf = pBuffer->buff;
    buf.len = pBuffer->nLen;
    if(::WSASend(pBuffer->pSocket->s,&buf,1,&dwBytes,&dwFlags,&pBuffer->ol,NULL)!=NO_ERROR){
        if(::WSAGetLastError()!=WSA_IO_PENDING)
            return FALSE;
    }
    return TRUE;
}

---------------------4 主函数---------------------