man3/rtime.3

   1 .\" Copyright 2003 walter harms (walter.harms@informatik.uni-oldenburg.de)
   2 .\" Distributed under GPL
   3 .\" Modified 2003-04-04 Walter Harms
   4 .\" <walter.harms@informatik.uni-oldenburg.de>
   5 .\"
   6 .\" Slightly polished, aeb, 2003-04-06
   7 .\"
   8 .TH RTIME 3 2003-04-04 "sunrpc" "RPC time function"
   9 .SH NAME
  10 rtime \- get time from a remote machine
  11 .SH SYNOPSIS
  12 .nf
  13 .B "#include <rpc/des_crypt.h>"
  14 .sp
  15 .BI "int rtime(struct sockaddr_in *" addrp ", struct rpc_timeval *" timep ,
  16 .BI "          struct rpc_timeval *" timeout );
  17 .fi
  18 .SH DESCRIPTION
  19 This function uses the Time Server Protocol as described in
  20 RFC\ 868 to obtain the time from a remote machine.
  21 .LP
  22 The Time Server Protocol gives the time in seconds since midnight 1900-01-01,
  23 and this function subtracts the appropriate constant in order to
  24 convert the result to seconds since midnight 1970-01-01, the Unix epoch.
  25 .LP
  26 When
  27 .I timeout
  28 is non-NULL, the udp/time socket (port 37) is used.
  29 Otherwise, the tcp/time socket (port 37) is used.
  30 .SH "RETURN VALUE"
  31 On success, 0 is returned, and the obtained 32-bit time value is stored in
  32 .IR timep->tv_sec .
  33 In case of error \-1 is returned, and
  34 .I errno
  35 is set appropriately.
  36 .SH ERRORS
  37 All errors for underlying functions
  38 .RB ( sendto (),
  39 .BR poll (),
  40 .BR recvfrom (),
  41 .BR connect (),
  42 .BR read ())
  43 can occur.
  44 Moreover:
  45 .TP
  46 .B EIO
  47 The number of returned bytes is not 4.
  48 .TP
  49 .B ETIMEDOUT
  50 The waiting time as defined in timeout has expired.
  51 .SH "EXAMPLE"
  52 This example requires that port 37 is up and open.
  53 You may check
  54 that the time entry within
  55 .I /etc/inetd.conf
  56 is not commented out.
  57 .br
  58 The program connects to a computer called 'linux'.
  59 Using 'localhost' does not work.
  60 The result is the localtime of the computer 'linux'.
  61 .sp
  62 .nf
  63 #include <stdio.h>
  64 #include <errno.h>
  65 #include <string.h>
  66 #include <time.h>
  67 #include <rpc/auth_des.h>
  68 #include <netdb.h>
  69
  70 int use_tcp = 0;
  71 char *servername = "linux";
  72
  73 int
  74 main(void)
  75 {
  76     struct sockaddr_in name;
  77     struct rpc_timeval time1 = {0,0};
  78     struct rpc_timeval timeout = {1,0};
  79     struct hostent *hent;
  80     int ret;
  81
  82     memset((char *) &name, 0, sizeof(name));
  83     sethostent(1);
  84     hent = gethostbyname(servername);
  85     memcpy((char *) &name.sin_addr, hent->h_addr, hent->h_length);
  86
  87     ret = rtime(&name, &time1, use_tcp ? NULL : &timeout);
  88     if (ret < 0)
  89         perror("rtime error");
  90     else
  91         printf("%s\\n", ctime((time_t *) &time1.tv_sec));
  92
  93     return 0;
  94 }
  95 .fi
  96 .SH "NOTES"
  97 Only IPV4 is supported.
  98 .LP
  99 Some
 100 .I in.timed
 101 versions only support TCP.
 102 Try the above example program with
 103 .I use_tcp
 104 set to 1.
 105 .LP
 106 Libc5 uses the prototype
 107 .br
 108 int rtime(struct sockaddr_in *, struct timeval *, struct timeval *);
 109 .br
 110 and requires
 111 .I <sys/time.h>
 112 instead of
 113 .IR <rpc/auth_des.h> .
 114 .SH "BUGS"
 115 .BR rtime ()
 116 in glibc <= 2.2.5 does not work properly on 64bit machines.
 117 .SH "SEE ALSO"
 118 .BR netdate (1),
 119 .BR ntpdate (1),
 120 .BR rdate (1),
 121 .BR inetd (8)