#include <rpc/auth_des.h>
int rtime(struct sockaddr_in *addrp, struct rpc_timeval *timep,
struct rpc_timeval *timeout);
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.
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>.
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>
static int use_tcp = 0;
static 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);
}