/***************************************************************/
/*   rdate for Motorola System V/68                            */
/*   Targeted and tested on Motorola System V/68 R3V8          */
/*   man rdate from Motorola Unix System V/88 R4V4             */
/****************************************************************
rdate(1M)            ADMINISTRATOR COMMANDS             rdate(1M)

NAME
     rdate - set system date from a remote host

SYNOPSIS
     rdate hostname

DESCRIPTION
     rdate sets the local date and time from the  hostname  given
     as an argument.  You must be super-user on the local system.
     Typically rdate can be inserted as part of a startup script.

EXAMPLE
     # /usr/local/bin/rdate timeserver
     timeserver Sun Oct 25 11:12:48 2015

                             TCP/IP                             1
****************************************************************/

#include <stdio.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

main(argc,argv)
int argc;
char *argv[];
{

        struct  sockaddr_in socketaddr;
        struct  servent *service;
        struct  hostent *host;
        int     socket_h;               /* socket handle */

        u_long  networktime;            /* network time */
        long    longtime;               /* Unix time */

        if (argc != 2)
        {
                printf("usage: rdate host\n");
                exit(1);
        }

        if ((host = gethostbyname(argv[1])) == NULL)
        {
                fprintf(stderr, "rdate: unknown host %s\n", argv[1]);
                fprintf(stderr, "rdate: %s must be speficied in /etc/hosts\n", argv[1]);
                exit(1);
        }

        if ((service = getservbyname("time","tcp")) == NULL)
        {
                fprintf(stderr, "rdate: time or tcp: service not available\n");
                exit(1);
        }

        if ((socket_h = socket(AF_INET, SOCK_STREAM, 0)) < 0)
        {
                fprintf(stderr, "rdate: socket: socket open error\n");
                exit(1);
        }

        memcpy(&socketaddr.sin_addr, host->h_addr, host->h_length);
        socketaddr.sin_family = host->h_addrtype;
        socketaddr.sin_port = service->s_port;

        if (connect(socket_h, &socketaddr, sizeof(socketaddr)) < 0)
        {
                close(socket_h);
                fprintf(stderr, "rdate: socket: socket connect error\n");
                exit(1);
        }

        if (read(socket_h, &networktime, 4) != 4)
        {
                close(socket_h);
                fprintf(stderr, "rdate: socket: socket read error\n");
                exit(1);
        }

        close(socket_h);

        /* Seconds at 1.1.1970 according to RFC868 is 220898800L */
        longtime = ntohl(networktime) - 2208988800L;

        if (stime(&longtime) != 0)
        {
                fprintf(stderr, "rdate: stime failed\n");
                exit(1);
        }

        printf("%s %s", host->h_name, ctime(&longtime));
        exit(0);
}