I'm trying to create an IOCP TCP client and my code looks as follows: 

**TCPClient.h:**

```
#pragma once

typedef struct 
{ 
    WSAOVERLAPPED Overlapped; 
    SOCKET Socket; 
    WSABUF wsaBuf; 
    char Buffer[1024];
    DWORD Flags;
    DWORD BytesSent;
    DWORD BytesToSend;
} PER_IO_DATA, * LPPER_IO_DATA; 

class TCPClient
{
public:
    TCPClient();
    ~TCPClient();

    bool Connect(const std::string strIpAddress, UINT32 uPort);
    bool Disconnect();
    bool SendCommand(const std::string strCommandName);
    bool ReceiveResponse();

private:
    static DWORD WINAPI ClientWorkerThread(LPVOID lpParameter);

private:
    SOCKET m_socket;
    PER_IO_DATA *m_pPerIoData;
};

```

**TCPClient.cpp:**

```
#include "StdAfx.h"
#include "TCPClient.h"

TCPClient::TCPClient() :
    m_pPerIoData(NULL)
{
}

TCPClient::~TCPClient()
{
}

bool TCPClient::Connect(const std::string strIpAddress, UINT32 uPort)
{
    WSADATA wsaData;
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != NO_ERROR)
        return false;

    HANDLE hCompletionPort = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 0);
    if (!hCompletionPort)
        return false;

    SYSTEM_INFO systemInfo;
    GetSystemInfo(&systemInfo);

    for (DWORD dwIndex = 0; dwIndex < systemInfo.dwNumberOfProcessors; dwIndex++)
    {
        HANDLE hThread = CreateThread(NULL, 0, ClientWorkerThread, hCompletionPort, 0, NULL);
        CloseHandle(hThread);
    }

    m_socket = WSASocket(AF_INET, SOCK_STREAM, IPPROTO_TCP, NULL, 0, WSA_FLAG_OVERLAPPED);
    if (m_socket == INVALID_SOCKET)
    {
        WSACleanup();

        return false;
    }

    sockaddr_in server;
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = inet_addr(strIpAddress.c_str());
    server.sin_port = htons(uPort);

    CreateIoCompletionPort((HANDLE)m_socket, hCompletionPort, 0, 0);

    if (WSAConnect(m_socket, (LPSOCKADDR)&server, sizeof(server), NULL, NULL, NULL, NULL) == SOCKET_ERROR)
    {
        WSACleanup();

        return false;
    }

    return true;
}

bool TCPClient::Disconnect()
{
    if (m_socket)
        closesocket(m_socket);

    WSACleanup();

    return true;
}

bool TCPClient::SendCommand(const std::string strCommandName)
{
    m_pPerIoData = new PER_IO_DATA;
    ZeroMemory(m_pPerIoData, sizeof(PER_IO_DATA));

    strcpy(m_pPerIoData->Buffer, strCommandName.c_str());

    m_pPerIoData->Overlapped.hEvent = WSACreateEvent();
    m_pPerIoData->Socket = m_socket;
    m_pPerIoData->wsaBuf.buf = m_pPerIoData->Buffer;
    m_pPerIoData->wsaBuf.len = strlen(m_pPerIoData->Buffer);
    m_pPerIoData->BytesToSend = m_pPerIoData->wsaBuf.len;

    DWORD dwNumSent;
    if (WSASend(m_socket, &(m_pPerIoData->wsaBuf), 1, &dwNumSent, 0, &(m_pPerIoData->Overlapped), NULL) == SOCKET_ERROR)
    {
        if (WSAGetLastError() != WSA_IO_PENDING)
        {
            delete m_pPerIoData;
            return 0;
        }
    }

    while (TRUE)
        Sleep(1000);

    return true;
}

bool TCPClient::ReceiveResponse()
{
    return true;
}

DWORD WINAPI TCPClient::ClientWorkerThread(LPVOID lpParameter)
{
    HANDLE hCompletionPort = (HANDLE)lpParameter;
    DWORD NumBytesRecv = 0;
    ULONG CompletionKey;
    LPPER_IO_DATA PerIoData;

    while (GetQueuedCompletionStatus(hCompletionPort, &NumBytesRecv, &CompletionKey, (LPOVERLAPPED*)&PerIoData, INFINITE))
    {
        if (!PerIoData)
            continue;

        if (NumBytesRecv == 0)
        {
            std::cout << "Server disconnected!\r\n\r\n";
        }
        else
        {
            // use PerIoData->Buffer as needed...
            std::cout << std::string(PerIoData->Buffer, NumBytesRecv);

            PerIoData->wsaBuf.len = sizeof(PerIoData->Buffer);
            PerIoData->Flags = 0;

            if (WSARecv(PerIoData->Socket, &(PerIoData->wsaBuf), 1, &NumBytesRecv, &(PerIoData->Flags), &(PerIoData->Overlapped), NULL) == 0)
                continue;

            if (WSAGetLastError() == WSA_IO_PENDING)
                continue;
        }

        closesocket(PerIoData->Socket);
        delete PerIoData;
    }

    return 0;
}

```

**main.cpp:**

```
#include "stdafx.h"
#include "TCPClient.h"

int main()
{
    TCPClient client;

    client.Connect("127.0.0.1", 8888);

    client.SendCommand("Hello command\r\n");

    return 0;
}

```

My use of "m\_pPerIoData" is clearly wrong because I'm newing every time I do SendCommand() and not deleting it properly.

* Q1. Where should I do m\_pPerIoData = new PER\_IO\_DATA?
* Q2. Does it make sense to have a pointer to PER\_IO\_DATA as a member variable?

**Edit 2:**

I've done some renaming (Client -> Connection) to my existing code above because it was confusing me.

**Some background:**

* I'm creating a DLL that is used to control an ECR (Electronic Cash Register) device connected via LAN (or serial port).
* The DLL provides an easy-to-use interfaces such as Connect(), Disconnect() and also some ECR specific commands including Logon(), Logoff(), ReadCard() etc.
* (Probably overkill for my application but...) I'd like to make use of IOCP in my DLL to send/receive data to/from ECR asynchronously.

My top level class looks something like this:

```
#pragma once

#include "Connection.h"
#include "Uncopyable.h"
#include "ConnectionFactory.h"
#include "CommandName.h"

class Ecr : private Uncopyable
{
public:
    Ecr(const std::string& rstrConnectionInfo)
        : m_spConnection(ConnectionFactory::CreateConnection(rstrConnectionInfo))
    {
        //Initialise();
    }

    ~Ecr()
    {
        //Shutdown();
    }

    bool Initialise()
    {
        if (!m_spConnection)
            return false;

        m_spConnection->Initialise();

        return true;
    }

    bool Shutdown()
    {
        if (!m_spConnection)
            return false;

        m_spConnection->Shutdown();

        return true;
    }

    bool Connect()
    {
        if (!m_spConnection)
            return false;

        if (!m_spConnection->Connect())
            return false;

        return true;
    }

    bool Disconnect()
    {
        m_spConnection->Disconnect();

        return true;
    }

    bool Logon(const std::vector<BYTE>& rvecCommandOptions)
    {
        m_spConnection->SendCommand(CommandName::Logon(), rvecCommandOptions);

        return true;
    }

    bool Logoff()
    {
        m_spConnection->SendCommand(CommandName::Logoff());

        return true;
    }

    // ... more commands follow.

private:
    ConnectionPtr m_spConnection;
};

```

And I've got TcpConnection class which is created by the ECR class and does all the hard work. Both Ecr and Connection classes are uncopyable.

**Connection.h:**

```
#pragma once

#include "Uncopyable.h"

class CommandName;

class Connection : private Uncopyable
{
public:
    Connection(const std::string& rstrConnectionInfo);
    virtual ~Connection();

    virtual bool Initialise() = 0;
    virtual bool Shutdown() = 0;
    virtual bool Connect() = 0;
    virtual bool Disconnect() = 0;
    virtual bool SendCommand(const CommandName& rCommandName, const std::vector<BYTE>& rvecCommandOptions) = 0;
    virtual bool ReceiveResponse() = 0;

    bool SendCommand(const CommandName& rCommandName);

private:
    std::string m_strConnectionInfo;
};

typedef std::tr1::shared_ptr<Connection> ConnectionPtr;

```

**TcpConnection.h:**

```
#pragma once
#include "connection.h"

class TcpConnection : public Connection
{
public:
    TcpConnection(const std::string& rstrConnectionInfo);
    ~TcpConnection();

    // Connection
    bool Initialise();
    bool Shutdown();
    bool Connect();
    bool Disconnect();
    bool SendCommand(const CommandName& rCommandName, const std::vector<BYTE>& rvecCommandOptions);
    bool ReceiveResponse();

    static DWORD WINAPI WorkerThread(LPVOID lpParam);

private:
    SOCKET m_socket;
    HANDLE m_hIocp;
};

```

**TcpConnection.cpp:**

```
#include "StdAfx.h"
#include "TcpConnection.h"
#include "CommandBuilderTcp.h"

TcpConnection::TcpConnection(const std::string& rstrConnectionInfo)
    : Connection(rstrConnectionInfo)
    , m_socket(INVALID_SOCKET)
    , m_hIocp(INVALID_HANDLE_VALUE)
{
    WSADATA wsaData;
    WSAStartup(MAKEWORD(2, 2), &wsaData);

    m_socket = WSASocket(AF_INET, SOCK_STREAM, IPPROTO_TCP, NULL, 0, WSA_FLAG_OVERLAPPED);
}

TcpConnection::~TcpConnection()
{
}

bool TcpConnection::Initialise()
{
    // Set up threads for using IOCP.

    m_hIocp = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 0);

    SYSTEM_INFO systemInfo;
    GetSystemInfo(&systemInfo);

    for (DWORD dwIndex = 0; dwIndex < systemInfo.dwNumberOfProcessors; dwIndex++)
    {
        HANDLE hThread = CreateThread(NULL, 0, WorkerThread, m_hIocp, 0, NULL);
        CloseHandle(hThread);
    }

    CreateIoCompletionPort((HANDLE)m_socket, m_hIocp, 0, 0);

    return true;
}

bool TcpConnection::Shutdown()
{
    // Release threads.

    return true;
}

bool TcpConnection::Connect()
{
    if (m_socket)
        return true;

    // Hard-coding IP address and port number for now.
    sockaddr_in server;
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = inet_addr("10.0.9.80");
    server.sin_port = htons(22000);

    WSAConnect(m_socket, (LPSOCKADDR)&server, sizeof(server), NULL, NULL, NULL, NULL);

    return true;
}

bool TcpConnection::Disconnect()
{
    if (m_socket)
        closesocket(m_socket);

    WSACleanup();

    return true;
}

bool TcpConnection::SendCommand(const CommandName& rCommandName, const std::vector<BYTE>& rvecCommandOptions)
{
    // Build full command from rCommandName and rvecCommandOptions and send to server.
    return true;
}

bool TcpConnection::ReceiveResponse()
{
    return true;
}

DWORD WINAPI TcpConnection::WorkerThread(LPVOID lpParam)
{
    // Call GetQueuedCompletionStatus in a loop
    return 0;
}

```

A host application then creates a DLL instance per ECR device:

```
Ecr ecr("ipaddress+port");

ecr.Initialise(); // Or do this in Ecr's ctor?

ecr.Connect();

BYTE arrCommandOptions[] = {0x00, 0x00, 0x00, 0x01, 0x18, 0xA6, 0x00, 0x01, 0x49, 0x08, 0x26};
std::vector<BYTE> vecCommandOptions(arrCommandOptions, arrCommandOptions + sizeof(arrCommandOptions) / sizeof(arrCommandOptions[0]));
ecr.Logon(vecCommandOptions);

ecr.Logoff();

ecr.Disconnect();

ecr.Shutdown(); // Or do this in Ecr's dtor?

return 0;

```

I want all the IOCP related stuff at the TcpConnection level, not the Ecr level because I don't want Ecr to care how data transmission is done underneath.

Is my idea not going to work?