使套接字服务器接受多个客户端

Question

我想更改我使用的socket class 以接受无限数量的客户。目前它允许一个客户端，一旦该客户端断开连接，服务器就会退出。

#include "stdafx.h"

#include "mySocket.h"
#include "myException.h"
#include "myHostInfo.h"

void main()
{

#ifdef WINDOWS_XP
    // Initialize the winsock library
    WSADATA wsaData;
    try
    {
        if (WSAStartup(0x101, &wsaData))
        {
            myException* initializationException = new myException(0,"Error: calling WSAStartup()");
            throw initializationException;
        }
    }
    catch(myException* excp)
    {
        excp->response();
        delete excp;
        exit(1);
    }
#endif

    // get local server information
    myHostInfo uHostAddress;
    string localHostName = uHostAddress.getHostName();
    string localHostAddr = uHostAddress.getHostIPAddress();
    cout << "------------------------------------------------------" << endl;
    cout << "   My local host information:" << endl;
    cout << "       Name:    " << localHostName << endl;
    cout << "       Address: " << localHostAddr << endl;
    cout << "------------------------------------------------------" << endl;

    // open socket on the local host
    myTcpSocket myServer(PORTNUM);
    cout << myServer;

    myServer.bindSocket();
    cout   << endl << "server finishes binding process... " << endl;

    myServer.listenToClient();
    cout   << "server is listening to the port ... " << endl;

    // wait to accept a client connection.
    // processing is suspended until the client connects
    cout   << "server is waiting for client connecction ... " << endl;

    myTcpSocket* client;    // connection dedicated for client communication
    string clientHost;      // client name etc.
    client = myServer.acceptClient(clientHost);

    cout   << endl << "==> A client from [" << clientHost << "] is connected!" << endl << endl;

    while(1)
    {
        //Send message to the client
        client->sendMessage(std::string("Test"));

        // receive from the client
        string clientMessageIn = "";
        int numBytes = client->recieveMessage(clientMessageIn); //Get message from client, non-blocking using select()
        if ( numBytes == -99 ) break;

        if(clientMessageIn != "")
        {
            std::cout << "received: " << clientMessageIn << std::endl; //What did we receive?

            /* Do somethign with message received here */
        }
    }

#ifdef WINDOWS_XP
    // Close the winsock library

    try
    {
        if (WSACleanup())
        {
            myException* cleanupException = new myException(0,"Error: calling WSACleanup()");
            throw cleanupException;
        }
    }
    catch(myException* excp)
    {
        excp->response();
        delete excp;
        exit(1);
    }

#endif
}

如何更改 main() 函数，以便它不断等待新客户端连接，一旦完成，为他（客户端）创建一个新线程，或者一个新的处理程序套接字（无论是什么)。

我确实发现this 线程提供了丰富的信息，但我缺乏在上述代码中实际实现它所需的套接字知识。

答案是When doing socket communication, you basically have a single listener socket for all incoming connections, and multiple handler sockets for each connected client.

所以我在我的代码中猜测；

myTcpSocket myServer(PORTNUM);
myServer.bindSocket();
myServer.listenToClient();

应该是listener socket

但是我将在哪里/如何分叉连接到 handler socket 的客户端？

我很抱歉我不能表现出更多的努力，我不喜欢给人懒惰的印象。但是对于我搜索的所有时间以及由此产生的反复试验，我没有太多可以展示的东西。

Answer 1

这个想法很简单，你只需等待传入的连接，一旦被接受，就将套接字传递给线程。

需要将accept返回的新socket传递给新线程；您可以每次都生成一个新线程并通过参数传递套接字，或者将套接字添加到一组工作线程使用的共享队列中。

这是我编写的一个简单代理的一些代码，它对线程使用 boost 并在套接字函数周围使用一个简单的 OOP 包装器。

主线程 - 它创建 4 个空闲并等待的工作线程 要发出信号的信号量。它将所有接受的连接推送到全局队列：

// Global variables

const size_t MAX_THREADS = 4;

queue<Socket> socketBuffer; // Holds new accepted sockets
boost::mutex queueGuard; // Guards the socketBuffer queue
semaphore queueIndicator; // Signals a new connection to the worker threads
bool ctrlc_pressed = false;

// Inside the main function...

boost::thread_group threads;
for(int i = 0; i < MAX_THREADS; i++)
{
    threads.create_thread(boost::bind(&threadHandleRequest, i+1));
}

while(!ctrlc_pressed)
{
    // wait for incoming connections and pass them to the worker threads
    Socket s_connection = s_server.accept();
    if(s_connection.valid())
    {
        boost::unique_lock<boost::mutex> lock(queueGuard);
        socketBuffer.push(s_connection);
        queueIndicator.signal();
    }
}

threads.interrupt_all(); // interrupt the threads (at queueGuard.wait())
threads.join_all(); // wait for all threads to finish

s_server.close();

还有线程代码：

bool threadHandleRequest(int tid)
{
    while(true)
    {
        // wait for a semaphore counter > 0 and automatically decrease the counter
        try
        {
            queueIndicator.wait();
        }
        catch (boost::thread_interrupted)
        {
            return false;
        }

        boost::unique_lock<boost::mutex> lock(queueGuard);

        assert(!socketBuffer.empty());

        Socket s_client = socketBuffer.front();
        socketBuffer.pop();

        lock.unlock();

        // Do whatever you need to do with the socket here
    }
}

希望有帮助:)

Answer 2

在进行套接字通信时，您基本上只有一个侦听器 所有传入连接的套接字，以及多个处理程序套接字 每个连接的客户端。

这就是重点。您需要一个单独的线程用于侦听器套接字。当它接收到传入请求时，它会为处理程序套接字启动另一个线程（它将创建并发送响应），然后再次开始侦听（您需要一个循环）。

我肯定会使用线程而不是分叉。 Windows 上的 AFAIK 只有 cygwin 能够分叉，但我不会将 cygwin 用于这样的程序。