rtime (3)
Leading comments
Copyright 2003 walter harms (walter.harms@informatik.uni-oldenburg.de) %%%LICENSE_START(GPL_NOVERSION_ONELINE) Distributed under GPL %%%LICENSE_END Modified 2003-04-04 Walter Harms <walter.harms@informatik.uni-oldenburg.de> Slightly polished, aeb, 2003-04-06
NAME
rtime - get time from a remote machineSYNOPSIS
#include <rpc/auth_des.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.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).| Interface | Attribute | Value |
| rtime() | Thread safety | MT-Safe |
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.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); }