我如何创建一个Boost.Asio服务器，可以同时处理多个客户端

如文档所述，

boost::asio::async_read(socket_, boost::asio::buffer(message_),

接受一个流函数

此外，它是一个异步操作，因此在发布读操作之后，在调用完成处理程序(handle_read)之前访问message_ 0 是有意义的。

我至少可以编译以下代码:

#include <ctime>
#include <iostream>
#include <string>
#include <boost/bind.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <boost/asio.hpp>
#include <json/reader.h>
#include <json/writer.h>
namespace {
    Json::Value to_json(std::string json)
    {
        Json::Value root;
        Json::Reader reader;
        /*bool success =*/ reader.parse(json, root);
        return root;
    }
    std::string to_string(Json::Value root) // unused TODO FIXME
    {
        Json::FastWriter writer;
        std::string json = writer.write(root);
        return json;
    }
}
using boost::asio::ip::tcp;
class tcp_connection : public boost::enable_shared_from_this<tcp_connection>
{
  public:
    typedef boost::shared_ptr<tcp_connection> pointer;
    static pointer create(boost::asio::io_service& io_service)
    {
        return pointer(new tcp_connection(io_service));
    }
    tcp::socket& socket()
    {
        return socket_;
    }
    void start()
    {
        //Read from client, make json and send appropriate response
        boost::asio::async_read(socket_, message_,
                boost::bind(&tcp_connection::handle_read, shared_from_this(),
                    boost::asio::placeholders::error,
                    boost::asio::placeholders::bytes_transferred));
    }
  private:
    tcp_connection(boost::asio::io_service& io_service)
        : socket_(io_service)
    {
    }
    void handle_write(const boost::system::error_code& /*error*/,
            size_t /*bytes_transferred*/)
    {
    }
    void handle_read(const boost::system::error_code& error, size_t bytes_transferred)
    {
        std::cout << "Handle Read of connectionn";
        if (error && error != boost::asio::error::eof) {
            std::cout << "Error: " << error.message() << "n";
            return;
        }
        std::string messageP;
        {
            std::stringstream ss;
            ss << &message_;
            ss.flush();
            messageP = ss.str();
        }
        std::cout << messageP << std::endl;
        Json::Value root      = to_json(messageP);
        std::string isHello   = root["hello"].asString();
        std::string isMessage = root["message"].asString();
        if(!isHello.empty())
        {
            std::string messageTemp = "{"Hello":"Server"}";
            boost::asio::async_write(socket_, boost::asio::buffer(messageTemp),
                    boost::bind(&tcp_connection::handle_write, shared_from_this(),
                        boost::asio::placeholders::error,
                        boost::asio::placeholders::bytes_transferred));
        }
        if(!isMessage.empty())
        {
            std::string messageTemp = "{"response":"Fine"}";
            boost::asio::async_write(socket_, boost::asio::buffer(messageTemp),
                    boost::bind(&tcp_connection::handle_write, shared_from_this(),
                        boost::asio::placeholders::error,
                        boost::asio::placeholders::bytes_transferred));
        }
    }
    tcp::socket socket_;
    boost::asio::streambuf message_;
};
class tcp_server
{
  public:
    tcp_server(boost::asio::io_service& io_service)
        : acceptor_(io_service, tcp::endpoint(tcp::v4(), 1936))
    {
        start_accept();
    }
  private:
    void start_accept()
    {
        tcp_connection::pointer new_connection =
            tcp_connection::create(acceptor_.get_io_service());
      acceptor_.async_accept(new_connection->socket(),
          boost::bind(&tcp_server::handle_accept, this, new_connection,
            boost::asio::placeholders::error));
    }
    void handle_accept(tcp_connection::pointer new_connection, const boost::system::error_code& error)
    {
        if (!error)
        {
            std::cout << "A client connected" << std::endl;
            new_connection->start();
        }
        start_accept();
    }
    tcp::acceptor acceptor_;
};
int main()
{
    try
    {
        boost::asio::io_service io_service;
        tcp_server server(io_service);
        io_service.run();
    }
    catch (std::exception& e)
    {
        std::cerr << e.what() << std::endl;
    }
}

您需要的包含。有些可能是不必要的:

boost/asio.hpp, boost/thread.hpp, boost/asio/io_service.hpp

boost/asio/spawn.hpp, boost/asio/write.hpp, boost/asio/buffer.hpp

vector, string.h, stdio.h, process.h, iterator

using namespace boost::asio;
using namespace boost::asio::ip;
io_service ioservice;
tcp::endpoint sim_endpoint{ tcp::v4(), 4066 };              //{which connectiontype, portnumber}
tcp::acceptor sim_acceptor{ ioservice, sim_endpoint };
std::vector<tcp::socket> sim_sockets;
static int iErgebnis;
int iSocket = 0;

void do_write(int a)                                        //gets the postion of the socket in the vector
{
    int iWSchleife = 1;                                     //to stay connected with putty or something
    static char chData[32000];
    std::string sBuf = "Received!rn";
    while (iWSchleife > 0)          
    {
        boost::system::error_code error;
        memset(chData, 0, sizeof(chData));
        iErgebnis = sim_sockets[a].read_some(boost::asio::buffer(chData), error);           //recv wie bei winsock. simulator empfängt
        iWSchleife = iErgebnis;                                                             //if iErgebnis is bigger then 0 it will stay in the loop. iErgebniss is always >0 when data is received
        if (iErgebnis > 0) {
            printf("%d Zeichen empf.vom Client : n%snn", iErgebnis, chData);
            write(sim_sockets[a], boost::asio::buffer(sBuf), error);
        }
        else {
            boost::system::error_code ec;
            sim_sockets[a].shutdown(boost::asio::ip::tcp::socket::shutdown_send, ec);       //close the socket when no data
            if (ec)
            {
                printf("studown error");                                                    // An error occurred.
            }
        }
    }
}
void do_accept(yield_context yield)
{
    while (1)                                                   //endless loop to accept limitless clients
    {
        sim_sockets.emplace_back(ioservice);                    //look to the link below for more info
        sim_acceptor.async_accept(sim_sockets.back(), yield);   //waits here to accept an client
        boost::thread dosome(do_write, iSocket);                //when accepts starts the thread do_write and passes the parameter iSocket
        iSocket++;                                              //to know the position of the socket in the vector
    }
}
int main()
{
    sim_acceptor.listen();
    spawn(ioservice, do_accept);            //here you can learn more about Coroutines https://theboostcpplibraries.com/boost.coroutine
    ioservice.run();                        //from here you jump to do:accept
    getchar(); 
}