server1.c

#include <stdio.h>
#include <string.h>    //strlen
#include <stdlib.h>    //strlen
#include <sys/socket.h>
#include <arpa/inet.h> //inet_addr
#include <unistd.h>    //write
#include <pthread.h> //for threading , link with lpthread

void *login_handler(void *);

int main(int argc , char *argv[])
{
    int flag=0 , socket_desc , new_socket , c , *new_sock;
    struct sockaddr_in server , client;
    char *message;

    //Create socket
    socket_desc = socket(AF_INET , SOCK_STREAM , 0);
    if (socket_desc == -1)
    {
        printf("Could not create socket");
    }

    //Prepare the sockaddr_in structure
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons( 8888 );

    //Bind
    if( bind(socket_desc,(struct sockaddr *)&server , sizeof(server)) < 0)
    {
        puts("bind failed");
        return 1;
    }
    puts("Bind done");

    //Listen
    listen(socket_desc , 3);

    //Accept and incoming connection
    puts("Waiting for incoming connections...");
    c = sizeof(struct sockaddr_in);
    while( (new_socket = accept(socket_desc, (struct sockaddr *)&client, (socklen_t*)&c)) )
    {
        puts("Connection accepted");

        //Reply to the client
        message = "Welcome,you are now connected.\n";
        write(new_socket , message , 2000);

        pthread_t sniffer_thread;
        new_sock = malloc(1);
        *new_sock = new_socket;
        if( pthread_create( &sniffer_thread , NULL ,  login_handler , (void*) new_sock) < 0)
        {
            perror("could not create thread");
            return 1;
        }
        while ( flag == 1 )
        {
             if( pthread_create( &sniffer_thread , NULL ,  login_handler , (void*) new_sock) < 0)
            {
            perror("could not create thread");
            return 1;
            }
        }
        //Now join the thread , so that we dont terminate before the thread
        //pthread_join( sniffer_thread , NULL);
        puts("Authentication progress iniciated.");


    }

    if (new_socket<0)
    {
        perror("accept failed");
        return 1;
    }

    return 0;
}

/*
 * This will handle connection for each client
 * */
void *login_handler(void *socket_desc)
{
    //Get the socket descriptor
    int sock = *(int*)socket_desc;
    int option , password , client_nummessage[2000];
    char username , *message , client_message[2000];

    //Send some messages to the client
    message = "Welcome to NTF.\n";
    write(sock , message , 2000);

    message = "What do you want to do?.\n";
    write(sock , message , 2000);

    message = "1-Login.\n2-Create new account.\n3-Exit NTF.\n";
    write(sock , message , 2000);

    //Receive a message from client
    recv(sock , client_nummessage , 1 , 0);

    if (*client_nummessage == 1)
    {
        puts("Login request.Requesting username and password.");

        message = "Please insert username.\n->";
        write(sock , message , 2000);

        recv(sock , client_message , 2000 , 0);
        //verificar se user existe. se existir,pedir passe.

        printf("%s",client_message);

        message = "Please insert password.\n->";
        write(sock , message , 2000);

        recv(sock , client_message , 5 , 0);
        //se a passe estiver correta,deu login no sistema. dar return 1 e passar a menu_handler.
        printf("%s",client_message);
    }

    else if (*client_nummessage == 2)
    {
        message = "Please insert desired username. \n->";
        write(sock , message , strlen(message));

        username = recv(sock , client_message , 2000 , 0);
        //verificar se o username existe. se existir, continuar.

        message = "Please insert password. \n->";
        write(sock , message , strlen(message));

        password = recv(sock , client_message , 2000 , 0);
        //verificar requerimentos da passe(opcional)

        //se ambas as credenciais estiverem corretas, repetir o login_handler.
    }

    else if (*client_nummessage == 3)
    {
        free(socket_desc);
    }

    else
    {
        message = "Invalid option. \n->";
        write(sock , message , strlen(message));
    }

    //Free the socket pointer
    free(socket_desc);

    return 0;
}