rtime(3)

1RTIME(3)                       RPC time function                      RTIME(3)
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NAME

6       rtime - get time from a remote machine
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SYNOPSIS

9       #include <rpc/des_crypt.h>
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11       int  rtime(struct sockaddr_in *addrp, struct rpc_timeval *timep, struct
12       rpc_timeval *timeout);
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DESCRIPTION

16       This function uses the Time Server Protocol as described in RFC 868  to
17       obtain the time from a remote machine.
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19       The  Time  Server  Protocol  gives  the  time in seconds since midnight
20       1900-01-01, and this function subtracts  the  appropriate  constant  in
21       order  to  convert the result to seconds since midnight 1970-01-01, the
22       Unix epoch.
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24       When timeout is non-NULL, the udp/time socket (port 37) is used.   Oth‐
25       erwise, the tcp/time socket (port 37) is used.
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RETURN VALUE

28       On success, 0 is returned, and the obtained 32-bit time value is stored
29       in timep->tv_sec.  In case of error -1 is returned, and  errno  is  set
30       appropriately.
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ERRORS

33       All errors for underlying functions (sendto(), poll(), recvfrom(), con‐
34       nect(), read()) can occur. Moreover:
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36       EIO    The number of returned bytes is not 4.
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38       ETIMEDOUT
39              The waiting time as defined in timeout has expired.
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EXAMPLE

42       This example requires that port 37 is up and open. You may  check  that
43       the time entry within /etc/inetd.conf is not commented out.
44       The  program  connects to a computer called 'linux'.  Using 'localhost'
45       does not work.  The result is the localtime of the computer 'linux'.
46
47       #include <stdio.h>
48       #include <errno.h>
49       #include <string.h>
50       #include <time.h>
51       #include <rpc/auth_des.h>
52       #include <netdb.h>
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54       int use_tcp = 0;
55       char *servername = "linux";
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57       int main() {
58         struct sockaddr_in name;
59         struct rpc_timeval time1 = {0,0};
60         struct rpc_timeval timeout = {1,0};
61         struct hostent *hent;
62         int ret;
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64         memset((char *)&name, 0, sizeof(name));
65         sethostent(1);
66         hent = gethostbyname(servername);
67         memcpy((char *)&name.sin_addr, hent->h_addr, hent->h_length);
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69         ret = rtime(&name, &time1, use_tcp ? NULL : &timeout);
70         if (ret < 0)
71           perror("rtime error");
72         else
73           printf("%s", ctime((time_t *)&time1.tv_sec));
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75         return 0;
76       }
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NOTES

79       Only IPV4 is supported.
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81       Some in.timed versions only support TCP. Try the above example  program
82       with use_tcp set to 1.
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84       Libc5 uses the prototype
85       int rtime(struct sockaddr_in *, struct timeval *, struct timeval *);
86       and requires <sys/time.h> instead of <rpc/auth_des.h>.
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BUGS

90       rtime() in glibc <= 2.2.5 does not work properly on 64bit machines.
91