Line-Following-Robot/Socket/lfr_socket.cpp

#include "lfr_socket.h"

LFR_Socket::LFR_Socket(ExceptionCallback cb): cb(cb)
{
    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    {
        throw std::runtime_error("Failed opening the socket");
    }

    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt)) != 0)
    {
        throw std::runtime_error("Failed setting the socket options");
    }

    address.sin_family = AF_INET;
    address.sin_addr.s_addr = INADDR_ANY;
    address.sin_port = htons(8080); 

    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address)) != 0)
    {
        throw std::runtime_error("Failed binding a name to the socket");
    }

    if (listen(server_fd, 0) != 0)
    {        
        throw std::runtime_error("Failed listening for connections");
    }
}

LFR_Socket::~LFR_Socket()
{
    endLoop();
    if (thread)
    {
        thread->join();
    }
}

void LFR_Socket::removeListener(LFR_Socket::ListenerKey key)
{
    std::lock_guard<std::mutex> lock(mutex);
    auto it = std::find_if(std::begin(listeners), std::end(listeners), [&](auto const &val){
        return val.first == key;
    });
    if(it != std::end(listeners))
    {
        listeners.erase(it);
    }
}

void LFR_Socket::addListener(LFR_Socket::ListenerCallback cb, LFR_Socket::ListenerKey key)
{
    std::lock_guard<std::mutex> lock(mutex);
    listeners.emplace_back(key, std::move(cb));
}

void LFR_Socket::setStop(bool val)
{
    std::lock_guard<std::mutex> lock(mutex);
    stop = val;
}

void LFR_Socket::createThread()
{
    thread = std::make_unique<std::thread>([this](){
        bool connected = false;
        while(true)
        {
            LFR_Socket::LFR_Telegram telegram;
            bool received = false;
            if(!stop && !listeners.empty())
            {
                try
                {
                    std::lock_guard<std::mutex> lock(mutex);

                    struct pollfd pollfds[2];
                    pollfds[0].fd = server_fd;
                    pollfds[0].events = POLLIN;
                    pollfds[1].events = POLLIN;
                    
                    if (poll(pollfds, 2, 200) > 0)
                    {
                        if(pollfds[0].revents & POLLIN || pollfds[1].revents & POLLIN)
                        {
                            if (!connected && pollfds[0].revents & POLLIN)
                            {
                                if ((new_socket = accept(server_fd, (struct sockaddr *)&address, (socklen_t *)&addrlen)) == -1)
                                {
                                    throw std::runtime_error("failed accepting connection");
                                }
                                else
                                {
                                    //std::cout << "accepted connection" << std::endl;
                                    pollfds[1].fd = new_socket;
                                    connected  = true;
                                }
                            }
                            else if (connected  && pollfds[0].revents & POLLIN)
                            {
                                //std::cout << "second connection incoming" << std::endl;
                                int tmp_socket = accept(server_fd, (struct sockaddr *)&address, (socklen_t *)&addrlen);
                                close(tmp_socket);
                                //std::cout << "second connection closed" << std::endl;
                            }
                            else if (pollfds[1].revents & POLLIN)
                            {
                                bytes_received = recv(new_socket, buffer, sizeof(buffer), 0);
                                if (bytes_received > 0)
                                {
                                    received = true;
                                    std::copy(std::begin(buffer), std::end(buffer), std::begin(telegram));
                                    //std::cout << "message received" << std::endl;
                                }
                                else if(bytes_received == 0)
                                {
                                    connected = false;
                                    close(pollfds[1].fd);
                                    //std::cout << "connection closed by peer" << std::endl;
                                }
                            }
                        }
                    }
                }
                catch(std::exception const &ex)
                {
                    if(!cb(ex))
                    {
                        //callback returned false -> exception not handled -> exit
                        exit(EXIT_FAILURE);
                    }
                }

                //Invoke the callback method (ListenerPair second -> ListenerCallback)
                if (received)
                {
                    for(auto &val : listeners)
                    {
                        val.second(telegram);
                    }
                }
            }
            else
            {
                break;
            }
            std::this_thread::sleep_for(std::chrono::milliseconds(150));
        }
    });
}

void LFR_Socket::startLoop()
{
    if(thread)
    {
        //Restart thread if it is running
        setStop(true);
        thread->join();
        setStop(false);
    }
    createThread();
}

void LFR_Socket::endLoop()
{
    setStop(true);
}