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 appropriate constant in order to convert the result to seconds since 00:00:00 UTC, 1 Jan 1970, the Unix Epoch.
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 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 <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
COLOPHON
This page is part of release 3.23 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/.
