rtime

RTIME(3)		      RPC time function			     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 midnight
       1900-01-01, and this function subtracts the  appropriate	 constant  in
       order  to convert the result to seconds since midnight 1970-01-01, the
       Unix epoch.

       When timeout is non-NULL, the udp/time socket (port 37) is used.	 Oth-
       erwise, 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, poll, recvfrom, connect,
       read) can occur. Moreover:

       ETIMEDOUT
	      The waiting time as defined in timeout has expired.

       EIO    The number of returned bytes is not 4.

EXAMPLE
       This example requires that port 37 is up and open. You may check	 that
       the time entry within /etc/inetd.conf is not commented 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 <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() {
	 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", ctime((time_t *)&time1.tv_sec));

	 return 0;
       }

NOTES
       Only IPV4 is supported.

       Some in.timed versions only support TCP. Try the above 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 does not work properly on 64bit machines.

SEE ALSO
       netdate(1), ntpdate(1), rdate(1), inetd(8)



sunrpc				  2003-04-04			     RTIME(3)