Boost ASIO Tcp 客户端/服务器 object 连接问题

Question

I'm trying to make an "connection handler" for Client and server the server-side works quite well with an other client but when i try to connect a client made the object, i've always the same crash and it appears right after the socket->connect .

this is the error from the client:

terminate called after throwing an instance of 'boost::wrapexcept<boost::system::system_error>'
  what():  bind: Address already in use

this is my TCP.cpp:

TCP::TCP(TYPE type)
{
    switch (type)
    {
        case (CLIENT):
            setup_client();
        case (SERVER):
            setup_server();
        default:
            break;
    }
}

TCP::~TCP()
{
    _socket->close();
}

void TCP::setup_client()
{
    boost::asio::ip::tcp::endpoint endpoint(boost::asio::ip::address::from_string("127.0.0.1"), PORT);
    _socket = new tcp::socket(_io_service);
    _socket->connect(endpoint);
}

void TCP::setup_server()
{
    _acceptor = new tcp::acceptor(_io_service, tcp::endpoint(tcp::v4(), PORT ));  //listen for new connection
    _socket = new tcp::socket(_io_service);  //socket creation 
    _acceptor->accept(*_socket);  //waiting for connection
}

string TCP::read_socket() {
    boost::asio::streambuf buf;
    boost::asio::read_until(*_socket, buf, "\n" );
    string data = boost::asio::buffer_cast<const char*>(buf.data());
    return data;
}

void TCP::send_socket(const string& message)
{
    const string msg = message + "\n";
    boost::asio::write(*_socket, boost::asio::buffer(message) );
}

and this my.hpp:

#define PORT 8080

enum TYPE {
    CLIENT,
    SERVER
};

class TCP {
    public:
        TCP(TYPE type);
        ~TCP();
        string read_socket();
        void send_socket(const string& message);

    protected:
    private:
        void setup_server();
        void setup_client();

        boost::asio::io_service _io_service;
        tcp::acceptor *_acceptor;
        tcp::socket *_socket;
};

Answer 1

You're missing a break statement:

TCP::TCP(TYPE type) {
    switch (type) {
    case (CLIENT):
        setup_client();
        break;
    case (SERVER):
        setup_server();
        break;
    default:
        break;
    }
}

This means that your client also tries to open an acceptor on the same port. That is normally not allowed.

Simplified

Removing a lot of bug sources:

Live On Coliru

#define PORT 8383
#include <boost/asio.hpp>
#include <iostream>
using namespace std::chrono_literals;
using boost::asio::ip::tcp;
using boost::system::error_code;

struct TCP {
    enum TYPE { CLIENT, SERVER };

    TCP(TYPE type);
    ~TCP();
    std::string read_socket();
    void send_socket(const std::string& message);

  private:
    boost::asio::io_service _io_service;
    tcp::socket _socket { _io_service };
    tcp::acceptor _acceptor { _io_service };
};

TCP::TCP(TYPE type) {
    if (type == CLIENT) {
        _socket.connect(tcp::endpoint{ {}, PORT});
    } else {
        _acceptor = tcp::acceptor{_io_service, {{}, PORT}};
        //_acceptor.bind({{}, PORT});
        _acceptor.accept(_socket);
    }
}

TCP::~TCP() {
    if (_socket.is_open())   _socket.close();
    if (_acceptor.is_open()) _acceptor.close();
}

std::string TCP::read_socket() {
    std::string data;
    auto n = read_until(_socket, boost::asio::dynamic_buffer(data), "\n");
    data.resize(n);
    return data;
}

void TCP::send_socket(const std::string& message) {
    write(_socket, boost::asio::buffer(message + "\n"));
}

int main() {
    std::thread server_th([&] {
        TCP s(TCP::SERVER);
        s.send_socket("ECHO: " + s.read_socket());
    });

    std::thread client_th([&] {
        std::this_thread::sleep_for(10ms);
        TCP c(TCP::CLIENT);
        c.send_socket("Hello world!");
        std::cout << c.read_socket() << "\n";
    });

    client_th.join();
    server_th.join();
}

Prints

ECHO: Hello world!