/udp_chat_server/Server.c

#include "Server.h"

/* accept or decline a connection request.
 * A new user gets accepted when the choosen name is not in the user list
 */
void
sendSV_CON_REP()
{
    ID = 2;
    uint8_t accepted = 1;
    uint16_t name_length;
    memcpy(&name_length, CL_CON_REQ + 1, sizeof(uint16_t));
    name_length = ntohs(name_length);

    char *name = malloc(name_length);
    strncpy(name, CL_CON_REQ + 3, name_length);
    /* Check if username already in list */

    if(find_username(name) == 1)
    {
        add_user(name);
        accepted = 0;

    }else accepted = 1;

    SV_CON_REP = malloc(sizeof(uint8_t) + sizeof(uint8_t) + sizeof(uint16_t));
    memcpy(SV_CON_REP, &ID, sizeof(uint8_t));
    memcpy(SV_CON_REP + 1, &accepted, sizeof(uint8_t));

    uint16_t cl_port = user->new_sv_sock_addr.sin_port;
    memcpy(SV_CON_REP + 2, &cl_port, sizeof(uint16_t));

    err = sendto(server_socket, SV_CON_REP, 4, 0, &from, sizeof(struct sockaddr_in));
    if (err == -1)
        printf("ERROR: Cannot send SV_CON_REP to client.\n");    

    if(accepted == 0)
    {
        sendSV_CON_AMSG();
    }
}


/* inform all users about the new client */
void 
sendSV_CON_AMSG()
{
    ID = 3;
    SV_CON_AMSG = malloc(strlen(user->name)+3);
    uint16_t name_length = htons(strlen(user->name));
    memcpy(SV_CON_AMSG, &ID, sizeof(uint8_t));
    memcpy(SV_CON_AMSG + 1, &name_length, sizeof(uint16_t));
    strncpy(SV_CON_AMSG + 3, user->name, strlen(user->name));

    sendToAll(SV_CON_AMSG, 3 + strlen(user->name));
}

/* build a recieved user message end send it to all users */
void 
sendSV_AMSG(struct user *sender)
{

    ID = 5;
    uint16_t name_length = htons(strlen(sender->name));
    
    uint32_t msg_length;
    memcpy(&msg_length, CL_MSG+1, sizeof(uint32_t));
    msg_length = ntohl(msg_length);
    char *msg = malloc(msg_length);
    strncpy(msg, CL_MSG+5, msg_length);

    SV_AMSG = malloc(7 + strlen(msg) + strlen(sender->name));
    
    msg_length = htonl(msg_length);
    memcpy(SV_AMSG, &ID, 1);
    memcpy(SV_AMSG+1, &name_length, 2);
    memcpy(SV_AMSG+3, sender->name, strlen(sender->name));
    memcpy(SV_AMSG+3+strlen(sender->name), &msg_length, 4);
    memcpy(SV_AMSG+7+strlen(sender->name), msg, ntohl(msg_length));
    
    sendToAll(SV_AMSG, 7 + strlen(sender->name) + ntohl(msg_length));
}

/* build char* SV_DISC_REP as response to CL_DISC_REQ */
void 
sendSV_DISC_REP(struct user *sender)
{
    ID = 7;
    SV_DISC_REP = malloc(1);
    memcpy(SV_DISC_REP, &ID, 1);
    int count;
    for (count = 0; count < 2; count ++)
    {
        to.sin_family = AF_INET;
        to.sin_port = htons(sender->port);
        to.sin_addr.s_addr = inet_addr(sender->IP);
        err = sendto(sender->sv_socket, SV_DISC_REP, 1, 0, &to, sizeof(struct sockaddr_in));
        if (err == -1)
        {
            printf("ERROR: Cannot send SV_DISC_REP to client.\n");    
            count += 1;
            sleep(5);    
        }
        else
            sendSV_DISC_AMSG(sender->name);
            remove_user(sender);
            break;
              
    }

}

/* build char *SV_DISC_AMSG to inform about client disconnect */
void 
sendSV_DISC_AMSG(char *name)
{
    ID = 8;
    uint16_t name_length;
    name_length = strlen(name);
    name_length = htons(name_length);

    SV_DISC_AMSG = malloc(3 + strlen(name));

    memcpy(SV_DISC_AMSG, &ID, 1);
    memcpy(SV_DISC_AMSG+1, &name_length, 2);
    strncpy(SV_DISC_AMSG+3, name, strlen(name));

    sendToAll(SV_DISC_AMSG, 3 + strlen(name));
    

}

/* send messages to all users in the list */
void
sendToAll(char *msg, int msg_length)
{
    struct user *receiver = user;
    int i;
    for (i = 0; i < usercount; i++)
    {   
        to.sin_family = AF_INET;
        to.sin_port = htons(receiver->port);
        to.sin_addr.s_addr = inet_addr(receiver->IP);
        err = sendto(receiver->sv_socket, msg, msg_length, 0, &to, sizeof(struct sockaddr_in));
        if (err == -1)
            printf("ERROR: Cannot send msg (ID: %i) to client.\n", atoi(msg[0])); 
        receiver = receiver->next;
    }
}


/* remove user from list, clear the associated socket and free allocated space */
void 
remove_user(struct user *leaver)
{
    struct user *tmp;
    tmp = user;
    int i;
    for (i = 0; i < usercount; i++)
    {
        if(tmp->name == leaver->name)
        {
            close(tmp->sv_socket);
            free(tmp);
            usercount --;
            break;

        }
        else if (tmp->next->name == leaver->name)
        {
            tmp->next = leaver->next;
            close(leaver->sv_socket);
            free(tmp->next);;
            usercount --;
            break;
        }
        else
            tmp = tmp->next;
    }
}


/*
 * checks wether username exists
 * @param name - the username to look for
 * return 1 - username doesn't exist
 * return 0 - username already exists
 */
int 
find_username(char *name)
{
    struct user *tmp = malloc(sizeof(struct user *));

    if(usercount == 0)
    {
        return 1;
    }
    else
    {   
        tmp = user;
        while(tmp->next != NULL)
        {
            if(strncmp(tmp->name, name, strnlen(name)) == 0)
            {
                return 0;
            }
            tmp = tmp->next;
        }
        return 1;
    }

}
/* add user 
 * @param name = username of the new_user user
 */
void 
add_user(char *name)
{
    new_user = malloc(sizeof(struct user));
   
    // set name
    strncpy(new_user->name, name, strlen(name));
    new_user->rep_counter;

    new_user->sv_socket = socket(AF_INET, SOCK_DGRAM, 0);

    strncpy(new_user->IP,inet_ntoa(from.sin_addr), strlen(inet_ntoa(from.sin_addr)));
    new_user->port = ntohs(from.sin_port);
    struct sockaddr_in sv_sock_add;
    sv_sock_add.sin_family = AF_INET;
    sv_sock_add.sin_port = 0;
    sv_sock_add.sin_addr.s_addr = inet_addr("127.0.0.1");

    new_user->new_sv_sock_addr = sv_sock_add;


    /* new_user port for the new_user client socket */
    err = bind(new_user->sv_socket, (struct sockaddr *) &new_user->new_sv_sock_addr, sizeof(struct sockaddr_in));    
    if(err < 0)
    {   
        perror("Bind error");
    }

    // set next user
    new_user->next = user;
    user = new_user;

    usercount += 1;

}

/* Portnumber validation */
int 
isValidPort(char *str)
{
    in_port_t tmp_port;
    tmp_port = atoi(str);
    if(tmp_port < 1024 || tmp_port > 65535)
    {
        printf("Invalid port number. Port hast do be between 1024 and 65535.\n");
        return 0;
    }
    printf("Valid port: %u\n", tmp_port);
    return 1;
}


/* Initialize field descriptors */
void 
init_fds()
{
    FD_ZERO(&readset);
    FD_SET(server_socket, &readset);
    
    struct user *tmp;
    tmp = user;
    
    highsock = server_socket;
    int i;
    for  (i = 0; i<usercount; i++)
    {
        FD_SET(tmp->sv_socket, &readset);
        if (tmp->sv_socket > highsock)
            highsock = tmp->sv_socket;
        tmp = tmp->next;

    }
}


int main(int argc, char**argv)
{

    /* Init user */
    user = malloc(sizeof(struct user));
    user = NULL;
    usercount = 0;

    time_to_wait = malloc(sizeof(struct timeval *));
    time_to_wait->tv_sec = 5;
    time_to_wait->tv_usec = 0;

    struct timeval *time_now = malloc(sizeof(struct timeval *));
    struct timeval *last_res = malloc(sizeof(struct timeval *));
    struct timeval *time_diff = malloc(sizeof(struct timeval *));


    
    int error;
    int flen;
    int rep_len;

    int c;
    int index;

    opterr = 0;

    while ((c = getopt(argc, argv, "p:")) != -1)
        switch(c)
            {
            case 'p':
                if (isValidPort(optarg) != 0)
                {
                    serv_port = atoi(optarg);
                    break;
                }
                return 1;
            case '?':
                if (optopt == 'p')
                    fprintf (stderr, "Option -%c requires an argument.\n", optopt);
                else if (isprint (optopt))
                    fprintf (stderr, "Unknown option `-%c'.\n", optopt);
                else
                    fprintf (stderr, "Unknown option character `\\x%x'.\n", optopt);
                return 1;
            default:
                abort ();
            }
    
    server_socket = socket(AF_INET, SOCK_DGRAM, 0);
    
    if (server_socket < 1)
    {
        perror("Create socket");
    } printf("Socket created!\n");
    
    /* set port and ip*/
    server_socket_address.sin_family = AF_INET;
    server_socket_address.sin_port = htons(serv_port);
    server_socket_address.sin_addr.s_addr = inet_addr("127.0.0.1");
    printf("IP Adresse: %s Port: %u\n", inet_ntoa(server_socket_address.sin_addr), ntohs(server_socket_address.sin_port));

    error = bind(server_socket, (struct sockaddr *) &server_socket_address, sizeof(struct sockaddr_in));
    
    if(error < 0)
    {   
        perror("Bind error");
    } else printf("Socket bound!\n");

    int res;
    int sock;
    time_now->tv_sec = time(NULL);
    while(1)
    {   

        ID = 0;
        init_fds();
        cl_rep_buffer = malloc(64);
        res = select(highsock + 1, &readset, NULL, NULL, time_to_wait);
        /* select error*/
        if (res == -1)
        {
            perror("Select Error.");
        }
        /* timeout. increase rep_counter for each connected user */
        else if (res == 0)
        {
            time_to_wait->tv_sec = 5;
            ID = 9;
            SV_PING_REQ = malloc(1);
            memcpy(SV_PING_REQ, &ID, sizeof(uint8_t));
            struct user *tmp;
            tmp = user;
            int i;
            for(i = 0; i<usercount; i++)
            {
                sendToAll(SV_PING_REQ, 1);
                tmp->rep_counter += 1;
                if(tmp->rep_counter == 4)
                {
                    printf("Verbindung zu User %s unterbrochen. Nutzr wird vom Server entfernt.\n", tmp->name);
                    remove_user(tmp);
                }
            }
        }
        
        else if (res > 0)
        {
            last_res->tv_sec = time(NULL);
            
            /* calc time diff  */ 
            timersub(time_now, last_res, time_diff); 

            timersub(time_to_wait, time_diff, time_to_wait);

            if (FD_ISSET(server_socket, &readset))
            {
                rep_len = recvfrom(server_socket, cl_rep_buffer, 64, 0, (struct sockaddr*) &from, &flen);
                memcpy(&ID, cl_rep_buffer, sizeof(uint8_t));
                if (ID == 1)
                {
                    printf("Anfrage gestellt.\n");
                    CL_CON_REQ = malloc(rep_len);
                    memcpy(CL_CON_REQ, cl_rep_buffer, rep_len);
                    sendSV_CON_REP();
                }
                else
                {
                    printf("Falsche Anfrage gestellt.\n");
                }
            }
                
           
            struct user *tmp;
            tmp = user;
            int i;
            
            for (i = 0; i < usercount; i++)
            {
                if(FD_ISSET(tmp->sv_socket, &readset))
                {   
                    rep_len = recvfrom(tmp->sv_socket, cl_rep_buffer, 64, 0, (struct sockaddr*) &from, &flen);
                    if(rep_len < 0)
                        break;
                    memcpy(&ID, cl_rep_buffer, sizeof(uint8_t));

                    switch(ID)
                    {           
                        
                        /* CL_MSG */
                        case 4:
                        {
                            CL_MSG = malloc(rep_len);
                            memcpy(CL_MSG, cl_rep_buffer, rep_len);
                            sendSV_AMSG(tmp);
                            break;
                        }

                        /* CL_DISC_REQ */
                        case 6:
                        {
                            CL_DISC_REQ = malloc(rep_len);
                            memcpy(CL_DISC_REQ, cl_rep_buffer, rep_len);
                            sendSV_DISC_REP(tmp);
                            break;
                        }

                        /* CL_PING_REP */
                        case 10:
                        {
                            // reset rep_counter
                            tmp->rep_counter = 0;
                        }
                        default:
                        {
                            break;
                        }
                    }
                }
                tmp = tmp->next;
            }
        }
              
    }    
}