tcp-number-guessing/109062273_ser.cpp

#include <iostream>
#include <sstream>
#include <string>
#include <cstring>
#include <cstdlib>
#include <ctime>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define BUFFER_SIZE 256
#define NOPORT_RET 10
#define INVALID_PORT_RET 20
#define BINDERR_RET 30
#define LISTENERR_RET 35

using namespace std;

class Game {
    private:
        int upper;
        int lower;
        int count;
        int answer;
    public:
        Game(void) {
            this->reset();
        }

        int get_upper() {
            return this->upper;
        }

        int get_lower() {
            return this->lower;
        }

        int get_count() {
            return this->count;
        }

        int get_answer() {
            return this->answer;
        }

        void reset() {
            this->upper = 999;
            this->lower = 0;
            this->count = 0;
            this->answer = rand() % 1000;
        }

        bool guess(int num) {
            this->count++;
            if (num == answer) return true;

            if (num > answer && num < this->upper) this->upper = num;
            else if (num < answer && num > this->lower) this->lower = num;

            return false;
        }
};

int main(int argc, char const *argv[]) {
    // initialize game
    srand(time(nullptr));
    Game game;

    // no port specified
    if (argc < 1) {
        cerr << "No port provided!" << endl << "Usage: server <port>" << endl;
        return NOPORT_RET;
    }

    int port = atoi(argv[1]);
    if (port < 0 || port >= 65536) {
        cerr << "Invalid port! port range: 0 ~ 65535" << endl;
        return INVALID_PORT_RET;
    }

    int sockfd = 0;
    struct sockaddr_in server_info;

    // create tcp socket
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd == -1) {
        cerr << "Failed to create socket" << endl;
    }

    // setup server info
    bzero((char *) &server_info, sizeof(server_info));
    server_info.sin_family = PF_INET;
    server_info.sin_addr.s_addr = INADDR_ANY;
    server_info.sin_port = htons(port);

    // bind
    if (bind(sockfd, (struct sockaddr *) &server_info, sizeof(server_info)) == -1) {
        cerr << "Cannot bind socker." << endl;
        close(sockfd);
        return BINDERR_RET;
    }

    // only one connection at the same time
    if (listen(sockfd, 1) == -1) {
        cerr << "Cannot listen to socket." << endl;
        return LISTENERR_RET;
    }
    cout << "Server up. Waiting connection..." << endl;

    int client_sockfd = 0;
    struct sockaddr_in client_info;
    socklen_t addrlen = sizeof(client_info);

    while (true) {
        client_sockfd = accept(sockfd, (struct sockaddr *) &client_info, &addrlen);
        if (client_sockfd < 0) {
            cout << "Error occurred while handling request from client." << endl;
            continue;
        }

        // retrieve client info
        char ip[INET_ADDRSTRLEN];
        uint16_t port;
        inet_ntop(AF_INET, &client_info.sin_addr, ip, sizeof(ip));
        port = ntohs(client_info.sin_port);

        cout << "New client from " << ip << ":" << port << " has connected!" << endl;

        // reset for new client
        game.reset();

        while (true) {
            // clear buffer for receive message
            char buffer[BUFFER_SIZE];
            memset(buffer, 0, sizeof(buffer));

            // wait message
            if (recv(client_sockfd, buffer, sizeof(buffer), 0) <= 0) {
                // closed connection
                cout << "Disconnected." << endl;
                break;
            }

            int guess = atoi(buffer);

            #ifdef DEBUG
            cout << guess << endl;
            #endif

            // message
            stringstream ss;
            const char * msg;

            #ifdef DEBUG
            cout << msg << endl;
            #endif

            // generate payload
            if (game.guess(guess)) {
                // win
                ss << game.get_answer() << ":" << game.get_answer() << ":" << game.get_count();

                // new turn for this client
                game.reset();
            } else {
                ss << game.get_lower() << ":" << game.get_upper() << ":" << game.get_count();
            }

            msg = ss.str().c_str();

            // send to client
            send(client_sockfd, msg, strlen(msg), 0);
        }
    }

    close(sockfd);
    return 0;
}