es5feb2010.c

# define errormsg(x) { puts(x); exit(1); }

int sendpkt(unsigned int timeout, char *ip, int port)
    {
    int sock;
    sock = socket(AF_INET, SOCK_DGRAM, 0);
    if(sock == -1) errormsg("Errore nella creazione del socket\n");

    struct sockaddr_in myaddr;
    myaddr.sin_family = AF_INET;
    myaddr.sin_port = htons(port);
    myaddr.sin_addr.s_addr = inet_aton(ip, &myaddr.sin_addr); // oppure: htonl(ip);

    char *senddata = malloc(sizeof(char) * 1024);
    memset(senddata, 0, 1024); // generizzazione di bzero
    char *recvdata = malloc(sizeof(char) * 1024);
    memset(recvdata, 0, 1024);

    int success;
    success = sendto(sock, senddata, 1024, 0, &myaddr, sizeof(myaddr));
    if(success == -1) errormsg("Invio fallito\n");

    signal(SIGALRM, failcase);
    alarm(timeout);
    success = recvfrom(sock, recvdata, 1024, 0, &myaddr, sizeof(myaddr));
    if(success == -1) errormsg("Ricezione fallita\n");

    int i = 1;
    int counter = 0;
    while(i < 1024)
        {
        if(*(recvdata + i) != *(senddata + i))
            counter++;
        i++;
        }

    return counter;
    }

int failcase(int sign)
    {
    if(sign == SIGALRM)
        return -1;
    }