C time server client error

noir911 · 06-28-2006, 05:41 AM

I just wrote a udp time client from Steven's TCP/IP Illustrated. The server the I am pointing to actually doesn't have a time server. But when I run the code it doesn't give any error & just sits there. Is it because I used "perror" instead of "err_sys" as described in the book? I tried using "err_sys" but it gives this error -

Code:

/tmp//ccx26364.o(.text+0x44): In function `main':
: undefined reference to `err_sys'

Code:

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#define BUFFSIZE 150

int
main()
{
    struct sockaddr_in serv;
    char buff[BUFFSIZE];
    int sockfd, n;

    if ((sockfd = socket (AF_INET, SOCK_DGRAM, 0)) < 0 )
//      err_sys ("socket error");
        perror ("socket error");
    bzero ((char *) &serv, sizeof (serv));

    serv.sin_family = AF_INET;
    serv.sin_addr.s_addr = inet_addr ("192.168.1.65");
    serv.sin_port = htons(13);

    if (sendto(sockfd, buff, BUFFSIZE, 0,
                (struct sockaddr *) &serv, sizeof(serv)) != BUFFSIZE)
        //      err_sys ("sendto error");
                perror ("sendto error");

    if (( n = recvfrom(sockfd, buff, BUFFSIZE, 0,
                    (struct sockaddr *) NULL, (int *) NULL )) < 2)
//      err_sys ("receive from error");
        perror ("reeive from error");

    buff [n-2] = 0;
    printf ("%s\n", buff);
    exit(0);
}

debulu · 06-28-2006, 06:30 AM

My friend the err_sys() call is defined by stevens in the appendix of the book and it is just a wrapper written by the great man. So that is not your problem. Even perror() should work fine. Just give a newline (\n) after the message of perror() and wait for some time while running. It may take a little time to decide the reachability of the host.
Second thing is remove the receive part form the program or exit after first perror(). May be it blocks at that recvfrom() call and sits there.

Code:

              if(sendto fails)
                 {
                    perror("Failed to establish con\n");
                    exit(0);
                  }

Hope helps