RTIME(3) | Linux Programmer's Manual | RTIME(3) |
NAME
rtime - get time from a remote machineSYNOPSIS
#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 appropriate 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 support only 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 commented out.#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(&name, 0, sizeof(name));
sethostent(1);
hent = gethostbyname(servername);
memcpy(&name.sin_addr, hent->h_addr, hent->h_length);
ret = rtime(&name, &time1, use_tcp ? NULL : &timeout);
if (ret < 0)
perror("rtime error");
else {
time_t t = time1.tv_sec;
printf("%s\n", ctime(&t));
}
exit(EXIT_SUCCESS);
}
SEE ALSO
ntpdate(1), inetd(8)COLOPHON
This page is part of release 3.53 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/.2012-08-03 | GNU |