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在调试时，当调用 WSARecv 时，我为函数提供PerIoData->WSABUF结构的地址。这应该将发送的数据分配给WSABUF.buf char* 数组，看起来是这样。当工作线程循环回到等待的GetQueuedCompletionStatus时，它似乎以某种方式（神奇地）将该数据发送到 PerIoData.Buffer （char* 数组）。所以本质上，PerIoData.Buffer和PerIoData.WSABUF.buf都等于同一个 char* 数组。当我从PER_IO_DATA结构（以及对它的所有引用）中删除PerIoData.Buffer时，尽管我知道客户端发送数据时GetQueuedCompletionStaus永远不会返回WSABUF.buf应该填充数据。

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  1. 我正在实现“Microsoft Windows 网络编程”（第 157 页）中的完成端口模型。尽管那本书中的示例还有很多有待独立发现，但我的代码现在可以正常工作了。
  2. ServerWorkerThread的while循环中：首先调用GetQueuedCompletionStatus，接收per_handle_data，per_io_data

  3. per_io_data 结构是这样的：

    struct _PER_IO_DATA{ //in the interests of an efficient question, i'm omitting the
//constructor/destructor code
public:
    OVERLAPPED Overlapped;
    WSABUF DataBuf;
    char myBuffer[BUFFER_LENGTH];
    int BufferLen;
    int OperationType;
};
typedef _PER_IO_DATA PER_IO_DATA;
typedef _PER_IO_DATA *PPER_IO_DATA;

  4. 我的 GetQueuedCompletionStatus 函数调用如下：

    ret = GetQueuedCompletionStatus(CompletionPort, &BytesTransferred, (LPDWORD)&PerHandleData, (LPOVERLAPPED *)&PerIoData, INFINITE);

  5. 我的 WSARecv 函数是这样调用的：

    WSARecv(PerHandleData->Socket, &(PerIoData->DataBuf), 1, NULL, &Flags, ((LPWSAOVERLAPPED)&PerIoData->Overlapped), NULL); //i know casting the Overlapped structure as LPWSAOVERLAPPED is unnecessary, but I was tweaking the //code when I didn't fully understand the problems I was having.

我的问题是我从来没有明确地为PerIoData->Buffer分配任何东西，但它似乎总是被发送的数据填充。我相信 GetQueuedCompletionStatus “知道”将此数据发送到该PerIoData->Buffer尽管它期望一个指向LPOVERLAPPED结构的指针（我将包含相关Buffer char 数组的PerIoData结构实例传递给该结构）。这真的让我很烦......也许它的行为不像我想的那样，但我可以看到PerIoData->Buffer被填充的唯一地方是来自GetQueuedCompletionStatus方法。如果不是这样，那么PerIoData->Buffer似乎无处不在？我已经搜索了 MSDN 和谷歌好几天了。我会继续寻找，如果我找到答案，我会发布更新。请帮忙？提前致谢！

*注意：我会创建标签 WSABUF 和 GetQueuedCompletionStatus，但这是我的第一篇文章。

--编辑：我发布了结构和工作线程，省略了所有其他不相关的代码。-- 您会注意到 _PER_IO_DATA::DataBuf.buf 已分配内存，然后归零。不指向 myBuffer 数组....

#include "stdafx.h"
#define SEND_POSTED 1
#define RECV_POSTED 2
#define BUFFER_LENGTH 1024

HANDLE CompletionPort;
SOCKADDR_IN serverAddress, *clientAddress;
SOCKET listener, client;
unsigned short port = 5000;
SYSTEM_INFO SystemInfo;
int i;

struct _PER_HANDLE_DATA{//Per handle data structure
    SOCKET Socket;
    SOCKADDR_STORAGE Address;
    _PER_HANDLE_DATA(){
        Socket = 0;
        ZeroMemory(&Address, sizeof(SOCKADDR_STORAGE));
    }
    ~_PER_HANDLE_DATA(){
        Socket = NULL;
        ZeroMemory(&Address, sizeof(SOCKADDR_STORAGE));
    }
};typedef _PER_HANDLE_DATA PER_HANDLE_DATA;typedef _PER_HANDLE_DATA *PPER_HANDLE_DATA;


struct _PER_IO_DATA{
public:
    OVERLAPPED Overlapped;
    WSABUF DataBuf;
    char myBuffer[BUFFER_LENGTH];
    int BufferLen;
    int OperationType;
    _PER_IO_DATA(){
        OperationType = 0;
        DataBuf.len = BUFFER_LENGTH;
        DataBuf.buf = (char*)malloc(BUFFER_LENGTH+1);
        BufferLen = BUFFER_LENGTH;
        ZeroMemory(DataBuf.buf, (sizeof(BUFFER_LENGTH+1)));
        ZeroMemory(&myBuffer, (sizeof(char)*BUFFER_LENGTH));
        SecureZeroMemory((PVOID)&Overlapped, sizeof(Overlapped));
    }
    ~_PER_IO_DATA(){
        free(&DataBuf.buf);
    }
};
typedef _PER_IO_DATA PER_IO_DATA;
typedef _PER_IO_DATA *PPER_IO_DATA;


unsigned _stdcall ServerWorkerThread(LPVOID CompletionPortID);

int _tmain(int argc, _TCHAR* argv[])
{
    /*
        INITIALIZE WINSOCK AND COMPLETION PORT, AND ACCEPT CONNECTIONS
    */
}

unsigned _stdcall ServerWorkerThread(LPVOID CompletionPortID){
    printf("ServerWorkerThread(%d) Working\n", GetCurrentThreadId());
    HANDLE CompletionPort = (HANDLE) CompletionPortID;
    DWORD BytesTransferred;
    PPER_HANDLE_DATA PerHandleData = new PER_HANDLE_DATA;
    PPER_IO_DATA PerIoData = new PER_IO_DATA;
    DWORD SendBytes = 0, RecvBytes = 0;
    DWORD Flags;
    BOOL ret;
    Sleep(2000);
    while(TRUE){
        ret = GetQueuedCompletionStatus(CompletionPort,
            &BytesTransferred,
            (LPDWORD)&PerHandleData,
            (LPOVERLAPPED *)&PerIoData,
            INFINITE);
        //printf("\n\nBytesTransferred: %d\n\n", BytesTransferred);
        if(BytesTransferred == 0 && (PerIoData->OperationType == RECV_POSTED || PerIoData->OperationType == SEND_POSTED)){
            closesocket(PerHandleData->Socket);
            GlobalFree(PerHandleData);
            GlobalFree(PerIoData);
            continue;
        }
        if(PerIoData->OperationType == RECV_POSTED){
        //output received data
            if(!strcmp(PerIoData->DataBuf.buf, "Disconnect") || !strcmp(PerIoData->DataBuf.buf, "disconnect")){
                printf("Disconnecting...\n");
                if(!shutdown(PerHandleData->Socket, SD_BOTH)){
                    closesocket(PerHandleData->Socket);
                    delete(PerHandleData);
                }
            }else{
                printf("RECV_POSTED: %s\n", PerIoData->DataBuf.buf);
            }
        }
        Flags = 0;

        SecureZeroMemory((PVOID)&PerIoData->Overlapped, sizeof(WSAOVERLAPPED));
        PerIoData->DataBuf.len = BUFFER_LENGTH;
        //***************************************************************************
        //Even though the following is commented out, PerIoData->DataBuf.buf 
        //is still being populated and so is PerIoData-myBuffer
        //So why is myBuffer being populated with data when DataBuf.buf is not pointing to it??
        //PerIoData->DataBuf.buf = PerIoData->myBuffer;
        //Also, if you comment out all references of myBuffer, GetQueuedCompletionStatus(),
        //will never return if myBuffer doesn't exist...how does it seem to be 'aware' of myBuffer?
        //***************************************************************************
        PerIoData->OperationType = RECV_POSTED;
        WSARecv(PerHandleData->Socket, &(PerIoData->DataBuf), 1, NULL, &Flags, ((LPWSAOVERLAPPED)&PerIoData->Overlapped), NULL);
    }
    return 0;
}
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