#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/wait.h>
#include <iostream>
using namespace std;

#define PORT 7777

extern int errno;

void sighandler(int signo){
    if(signo == SIGCHLD){
        cout<<"[server-"<<getpid()<<"]Child terminated\n";
        while(waitpid(-1, NULL, WNOHANG)>0);
    }
}

int main()
{
    struct sockaddr_in server;
    struct sockaddr_in from;
    string msg;
    string answer;
    char buf[1024];
    int n = 0;
    int sd;
    int optval = 1;

//----->socket()
    if((sd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    {
        perror("[server]Socket() error.\n");
        return errno;
    }

    setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval));

    bzero(&server, sizeof(server));
    bzero(&from, sizeof(from));

    server.sin_family = AF_INET;
    server.sin_addr.s_addr = htonl(INADDR_ANY);
    server.sin_port = htons(PORT);

//---->bind()
    if(bind(sd, (struct sockaddr*) &server, sizeof(struct sockaddr)) ==-1)
    {
        perror("[server]Bind() error.\n");
        return errno;
    }

//---->listen()
    if(listen(sd, 5) == -1)
    {
        perror("[server]Listen() error.\n");
        return errno;
    }

    cout<<"[server-"<<getpid()<<"]Waiting at the port "<<PORT<<endl;

    signal(SIGCHLD, SIG_IGN);

    while(1)
    {
        int client;
        socklen_t length = sizeof(from);
        int pid; //procesul copil
        char address[INET_ADDRSTRLEN]; // IP Client

        bzero(&from, sizeof(from));

//---->accept()
        client=accept(sd, (struct sockaddr*) &from, &length);

        if(client<0)
        {
            perror("[server]Accept() error.\n");
            continue;
        }
        else
        {
            inet_ntop(AF_INET, &from.sin_addr.s_addr, address, INET_ADDRSTRLEN);
            cout<<"[server-"<<getpid()<<"]The client connected: ";
            cout<<address<<':'<<ntohs(from.sin_port)<<endl;
        }

//---->fork()
        if((pid=fork())<0)
        {
            perror("fork() error");
            continue;
        }
        else if(pid ==0)
        {
            msg.empty();
            cout<<"[server-"<<getpid()<<"]Waiting a message...\n";

            bzero(buf, 500);

            while((n=recv(client, buf, sizeof(buf), 0))>0)
            {
                msg.append(buf, buf+n);
            }

            if(n<0)
            {
                cout<<"[server-"<<getpid()<<"]Read from client error.\n";
                close(client);
                continue;
            }

            cout<<"[server-"<<getpid()<<"]Message received: "<<msg<<endl;

            answer.empty();
            answer="Hello "+msg;

            cout<<"[server-"<<getpid()<<"]Sending message back..."<<answer<<endl;

            if(n = (send(client, answer.data(), answer.size(), 0))<0)
            {
                cout<<"[server-"<<getpid()<<"]Write to client error\n";
                continue;
            }
            else
                cout<<"[server-"<<getpid()<<"]Message successfully sent\n";

            close(client);

            exit(0);
        } /*fork()*/

        close(client);

    }   /*while*/
}   /*main*/