#!/usr/local/bin/perl
#
# 5/1999 J.E. Klasek jk AT auto tuwien ac at
# 
# V 1.0
#
# Description:
#	Get remote time from TCP/IP time service 
#	 
# Syntax:
#	check_time [-v] [server]
#
# Parameter:
#	-v	be verbose
#
# Exit status:
#	0	ok, server process responded
#	<>0	server or server process not reachable/existing
#
# Revisions:
#	2010-12-28 J.E. Klasek 
#		Fixed: recv() return value handling.
#		Beautified.


use Socket;

$timeout = 10;		# timeout for server response
$port = "time";		# time server port


# argument parsing

while ( $_ = $ARGV[0], /^-/ ) {
	shift;
#	if (/^-o/) {
#		if ($ARGV[0]) {
#			$tm_file = $ARGV[0];
#			shift;
#			next;
#		}
#	}
	/^-v/ && ( $verbose = 1, next );
usage: {
	print "Usage: $0 [-v][server]\n", <<EOT
	Exit status 0 means server process available, other the process
	or host does not exist.
	-v	print verbose output instead of be silent
EOT
	;
	exit (1);
	}

}


# get servername, if non available use localhost (done below)
if (defined($ARGV[0])) { $server = $ARGV[0]; shift; }

$server = 'localhost' unless $server;


chop($hostname = `hostname`);

($name, $aliases, $proto) = getprotobyname('tcp');
($name, $aliases, $port) = getservbyname($port, 'tcp')
unless $port =~ /^\d+$/;
($name, $aliases, $type, $len, $thisaddr) =
gethostbyname($hostname);
(($name, $aliases, $type, $len, $thataddr) = gethostbyname($server)) || die "host $server unkown.\n";

$sthis = sockaddr_in(0,$thisaddr);
$sthat = sockaddr_in($port,$thataddr);

#DEBUG	  print STDERR "foreign: socket, $port, server=$server, name=$name, type=$type, len=$len, thataddr=".sprintf("0x%X",unpack("N",$thataddr))."\n";

socket(S, PF_INET, SOCK_STREAM, $proto) || die "socket: $!\n";
if ($verbose) { print "connecting to $server\n"; }
connect(S, $sthat) || die "connect: $!\n";

select(S); $| = 1; select(stdout);		# socket unbuffered

vec($rbits, fileno(S), 1) = 1;
if ($verbose) { print "waiting for a request from $server\n"; }
$resp = select($rout=$rbits,undef,undef,$timeout);
if ($resp == 0) {
		print "connection timed out";
		close(S);
		exit 1;
}
$ltime = time();
recv(S,$rtime,4,0);
if (length($rtime) != 4) {
		die "Server data incomplete!\n";;
} 

# remote time is elapsed seconds since 1.1.1900, take offset to 1.1.1970 into
# account (UNIX time)
$currenttime = unpack("N",$rtime)-2208988800;
print "remote time, seconds since 1.1.1970 00:00 = ".$currenttime."\n";
print "local time, seconds since 1.1.1970 00:00 = ".$ltime."\n";
	
print "remote date = ".localtime($currenttime)."\n";
print "local date = ".localtime($ltime)."\n";

print "deviation local - remote (s) = ".($ltime - $currenttime)."\n";


close(S);

exit 0;