RTIME(3)                                            Linux Programmer's Manual                                           RTIME(3)



NAME
       rtime - get time from a remote machine

SYNOPSIS
       #include <rpc/des_crypt.h>

       int rtime(struct sockaddr_in *addrp, struct rpc_timeval *timep,
                 struct rpc_timeval *timeout);

DESCRIPTION
       This function uses the Time Server Protocol as described in RFC 868 to obtain the time from a remote machine.

       The Time Server Protocol gives the time in seconds since 00:00:00 UTC, 1 Jan 1900, and this function subtracts the appro-
       priate constant in order to convert the result to seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).

       When timeout is non-NULL, the udp/time socket (port 37) is used.  Otherwise, the tcp/time socket (port 37) is used.

RETURN VALUE
       On success, 0 is returned, and the obtained 32-bit time value is stored  in  timep->tv_sec.   In  case  of  error  -1  is
       returned, and errno is set appropriately.

ERRORS
       All errors for underlying functions (sendto(2), poll(2), recvfrom(2), connect(2), read(2)) can occur.  Moreover:

       EIO    The number of returned bytes is not 4.

       ETIMEDOUT
              The waiting time as defined in timeout has expired.

NOTES
       Only IPv4 is supported.

       Some in.timed versions only support TCP.  Try the example program with use_tcp set to 1.

       Libc5 uses the prototype
       int rtime(struct sockaddr_in *, struct timeval *, struct timeval *);
       and requires <sys/time.h> instead of <rpc/auth_des.h>.

BUGS
       rtime() in glibc 2.2.5 and earlier does not work properly on 64-bit machines.

EXAMPLE
       This  example requires that port 37 is up and open.  You may check that the time entry within /etc/inetd.conf is not com-
       mented out.
       The program connects to a computer called "linux".  Using "localhost" does not work.  The result is the localtime of  the
       computer "linux".

       #include <stdio.h>
       #include <stdlib.h>
       #include <errno.h>
       #include <string.h>
       #include <time.h>
       #include <rpc/auth_des.h>
       #include <netdb.h>

       int use_tcp = 0;
       char *servername = "linux";

       int
       main(void)
       {
           struct sockaddr_in name;
           struct rpc_timeval time1 = {0,0};
           struct rpc_timeval timeout = {1,0};
           struct hostent *hent;
           int ret;

           memset((char *) &name, 0, sizeof(name));
           sethostent(1);
           hent = gethostbyname(servername);
           memcpy((char *) &name.sin_addr, hent->h_addr, hent->h_length);

           ret = rtime(&name, &time1, use_tcp ? NULL : &timeout);
           if (ret < 0)
               perror("rtime error");
           else
               printf("%s\n", ctime((time_t *) &time1.tv_sec));

           exit(EXIT_SUCCESS);
       }

SEE ALSO
       ntpdate(1), inetd(8)

COLOPHON
       This  page  is  part of release 3.25 of the Linux man-pages project.  A description of the project, and information about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



GNU                                                        2010-02-25                                                   RTIME(3)