host/ihost-perl/ihost.pl

#!/usr/bin/perl -w

# -----------------------------------------------------------
# Perl i-scream Host.
# http://www.i-scream.org.uk
#
# An all-in-one script to act as an i-scream host on
# a typical Unix/Linux box.  You may adapt the data-gathering
# methods as you see fit.
#  - pjm2@ukc.ac.uk
#
# $Author: pjm2 $
# $Id: ihost.pl,v 1.28 2001/03/14 18:48:33 pjm2 Exp $
#------------------------------------------------------------

$| = 1;

use strict;
use IO::Socket;
use Sys::Hostname;

use vars qw (
             $filter_manager_addr
             $filter_manager_port
             $seq_no
             $udp_update_time
             $tcp_update_time
             $last_udp_time
             $last_tcp_time
             $last_modified
             $udp_port
             $tcp_port
             $filter_addr
             $file_list
             $fqdn
             $pidfile
             $retry_wait
            );

if (@ARGV != 2) {
    die "Usage: ihost.pl [i-scream filter manager] [TCP port]\n";
}

$filter_manager_addr = $ARGV[0];
$filter_manager_port = $ARGV[1];

$seq_no = 1;
$retry_wait = 600;

# write our PID to a file
$pidfile = "/var/tmp/ihost.pid";
&write_pid();

&tcp_configure();
&send_udp_packet();

$last_udp_time = time;
$last_tcp_time = time;
while (1) {
    my($time) = time;
    if ($time >= $last_udp_time + $udp_update_time) {
        &send_udp_packet();
        $last_udp_time = $time;
    }
    if ($time >= $last_tcp_time + $tcp_update_time) {
        &send_tcp_heartbeat();
        $last_tcp_time = $time;
    }
    my($next_udp) = $udp_update_time - $time + $last_udp_time;
    my($next_tcp) = $tcp_update_time - $time + $last_tcp_time;
    my($delay);
    if ($next_udp < $next_tcp) {
        $delay = $next_udp
    }
    else {
        $delay = $next_tcp;
    }
    `sleep $delay`;
}

# we'll probably never get here...
`rm -f $pidfile`;
exit(0);


#-----------------------------------------------------------------------
# wait_then_retry
# Waits for the period of time specified in $retry_wait, then attempts
# to reconfigure with the server.
#-----------------------------------------------------------------------
sub wait_then_retry() {
    print "Will retry configuration with filter manager in $retry_wait seconds.\n";
    `sleep $retry_wait`;
}


#-----------------------------------------------------------------------
# tcp_configure
# Establishes a TCP connection to the specified i-scream filter manager.
# The host then requests details from the server, such as the intervals
# at which to send UDP packets.
#-----------------------------------------------------------------------
sub tcp_configure() {
    
    while (1 == 1) {
        my($sock) = new IO::Socket::INET(
                                         PeerAddr => $filter_manager_addr,
                                         PeerPort => $filter_manager_port,
                                         Proto => 'tcp'
                                        ) or die "Cannot connect!";
        if (!defined $sock) {
            print "IHOST ERROR: Could not connect to $filter_manager_addr:$filter_manager_port.\n";
            print "Please check that there is an i-scream server at this address.\n";
            close($sock);
            wait_then_retry();
            next;
        }

        # Now run through the configuration process...
        my($response);
    
        print $sock "STARTCONFIG\n";
        $response = <$sock>;
        if (!chop $response eq "OK") {
            print "The i-scream server rejected the STARTCONFIG command.  Terminated.";
            close($sock);
            wait_then_retry();
            next;
        }

        print "Config started okay.\n";
    
        print $sock "LASTMODIFIED\n";
        $response = <$sock>;
        chop $response;
        $last_modified = $response;
    
        print "Config last modified: ". (scalar localtime $last_modified/1000) . "\n";

        print $sock "FILELIST\n";
        $response = <$sock>;
        chop $response;
        $file_list = $response;

        print "File list obtained: $file_list\n";

        print $sock "FQDN\n";
        $response = <$sock>;
        chop $response;
        $fqdn = $response;

        print "FQDN returned: $fqdn\n";

        print $sock "UDPUpdateTime\n";
        $response = <$sock>;
        chop $response;
        $udp_update_time = $response;

        print $sock "TCPUpdateTime\n";
        $response = <$sock>;
        chop $response;
        $tcp_update_time = $response;
    
        print "UDP packet period: $udp_update_time seconds.\nTCP heartbeat period: $tcp_update_time seconds.\n";

        print $sock "ENDCONFIG\n";
        $response = <$sock>;
        chomp $response;
        if (!$response eq "OK") {
            print "ENDCONFIG command to server failed.  Terminated.\n";
            close($sock);
            wait_then_retry();
            next;
        }

        print "Config ended.\n";
    
        print $sock "FILTER\n";
        $response = <$sock>;
        unless (defined($response)) {
            print "Failed: Could not get a filter address from the filter manager.\n";
            close($sock);
            wait_then_retry();
            next;
        }
        chop $response;
        $response =~ /(.*);(.*);(.*)/;
        if ($response eq "ERROR") {
            print "There are no active configured filters for your host.\n";
            close($sock);
            wait_then_retry();
            next;
        }
        ($filter_addr, $udp_port, $tcp_port) = ($1, $2, $3);
        unless (defined($filter_addr) && defined($udp_port) && defined($tcp_port)) {
            print "Failed: Filter address response from server did not make sense: $response\n";
            close($sock);
            wait_then_retry();
            next;
        }
    
        print "Got filter data ($filter_addr, $udp_port, $tcp_port)\n";

        print $sock "END\n";
        $response = <$sock>;
        chop $response;
        if ($response eq "OK") {
            print "Host successfully configured via TCP.\n"
        }
        else {
            print "The server failed the host configuration on the END command.";
            close($sock);
            wait_then_retry();
            next;
        }
    
        close($sock);

        print "Configuration finished sucessfully!\n";
        last;
    }
    return;
}


#-----------------------------------------------------------------------
# send_udp_packet
# Sends a UDP packet to an i-scream filter.
# The packet contains XML markup describing some of the machine's state.
# Receipt of UDP packets is not guaranteed.
#-----------------------------------------------------------------------
sub send_udp_packet() {

    my(@statgrab) = `./statgrab.pl`;
    my(%packet);
    for (my($i) = 0; $i <= $#statgrab; $i++) {
        $statgrab[$i] =~ /^([^\s]*) (.*)$/;
        $packet{$1} = $2;
    }
    
    my($date) = time;
    
    my($disk_info) = "<disk>";
    my($i) = 0;
    while (defined $packet{"packet.disk.p$i.attributes.mount"}) {
        $disk_info .= "<p$i";
        $disk_info .= " name=\"" . $packet{"packet.disk.p$i.attributes.name"} . "\"";
        $disk_info .= " kbytes=\"" . $packet{"packet.disk.p$i.attributes.kbytes"} . "\"";
        $disk_info .= " used=\"" . $packet{"packet.disk.p$i.attributes.used"} . "\"";
        $disk_info .= " avail=\"" . $packet{"packet.disk.p$i.attributes.avail"} . "\"";
        $disk_info .= " mount=\"" . $packet{"packet.disk.p$i.attributes.mount"} . "\"";
        $disk_info .= "></p$i>";
        ++$i;
    }
    $disk_info .= "</disk>";

    my($ip) = inet_ntoa(scalar(gethostbyname(hostname())) || 'localhost');

    # Build the XML packet this way, as we can clearly
    # see the structure and contents... I like this ;-)
    # [Note that the server rejects UDP packets that are
    # larger than 8196 bytes]
    my($xml) = <<EOF;
    
<packet seq_no="$seq_no" machine_name="$fqdn" date="$date" type="data" ip="$ip">
    <load>
        <load1>$packet{"packet.load.load1"}</load1>
        <load5>$packet{"packet.load.load5"}</load5>
        <load15>$packet{"packet.load.load15"}</load15>
    </load>
    <os>
        <name>$packet{"packet.os.name"}</name>
        <release>$packet{"packet.os.release"}</release>
        <platform>$packet{"packet.os.platform"}</platform>
        <sysname>$packet{"packet.os.sysname"}</sysname>
        <version>$packet{"packet.os.version"}</version>
        <uptime>$packet{"packet.os.uptime"}</uptime>
    </os>
    <users>
        <count>$packet{"packet.users.count"}</count>
        <list>$packet{"packet.users.list"}</list>
    </users>
    <processes>
        <total>$packet{"packet.processes.total"}</total>
        <sleeping>$packet{"packet.processes.sleeping"}</sleeping>
        <zombie>$packet{"packet.processes.zombie"}</zombie>
        <stopped>$packet{"packet.processes.stopped"}</stopped>
        <cpu>$packet{"packet.processes.cpu"}</cpu>
    </processes>
    <cpu>
        <idle>$packet{"packet.cpu.idle"}</idle>
        <user>$packet{"packet.cpu.user"}</user>
        <kernel>$packet{"packet.cpu.kernel"}</kernel>
        <iowait>$packet{"packet.cpu.iowait"}</iowait>
        <swap>$packet{"packet.cpu.swap"}</swap>
    </cpu>
    <memory>
        <total>$packet{"packet.memory.total"}</total>
        <free>$packet{"packet.memory.free"}</free>
    </memory>
    <swap>
        <total>$packet{"packet.swap.total"}</total>
        <free>$packet{"packet.swap.free"}</free>
    </swap>
    $disk_info
</packet>

EOF

    # Make the packet smaller by stripping out newlines and leading spaces.
    $xml =~ s/\n\s*//g;

    my($sock) = new IO::Socket::INET (
                                      PeerPort => $udp_port,
                                      PeerAddr => $filter_addr,
                                      Proto => 'udp'
                                     ) or die "Could not send UDP: $!\n";

    print $sock $xml or die "Could not send UDP packet: $!\n";
    close($sock);
    $seq_no++;
    print "-";
    
    return;
}


#-----------------------------------------------------------------------
# send_tcp_heartbeat
# Establishes a TCP connection to an i-scream filter.
# The heartbeat is used as a guaranteed "I'm alive" delivery mechanism.
#-----------------------------------------------------------------------
sub send_tcp_heartbeat() {

    my($sock) = new IO::Socket::INET(
                                     PeerAddr => $filter_addr,
                                     PeerPort => $tcp_port,
                                     Proto => 'tcp'
                                    ) or return;
    if (!defined $sock) {
        print "IHOST WARNING: Failed to deliver a heartbeat to the i-scream filter.\n";
        &tcp_configure();
        return;
    }

    # Now run through the configuration process.
    my($response);

    print $sock "HEARTBEAT\n";
    $response = <$sock>;
    return if (!defined $response);
    chop $response;
    if (!$response eq "OK") {
        close($sock);
        print "Server gave wrong response to HEARTBEAT: $response\n";
        &tcp_configure();
        return;
    }
    
    print $sock "CONFIG\n";
    $response = <$sock>;
    return if (!defined $response);
    chop $response;
    if (!$response eq "OK") {
        close($sock);
        print "Server gave wrong response to CONFIG: $response\n";
        &tcp_configure();
        return;
    }

    print $sock "$file_list\n";
    $response = <$sock>;
    return if (!defined $response);
    chop $response;
    if (!$response eq "OK") {
        close($sock);
        print "Server gave wrong response to file list: $response\n";
        &tcp_configure();
        return;
    }
    
    print $sock "$last_modified\n";
    $response = <$sock>;
    return if (!defined $response);
    chop $response;
    if ($response eq "ERROR") {
        close($sock);
        print "Server configuration changed.  Reconfiguring with filter manager.\n";
        &tcp_configure();
        return;
    }
    if (!$response eq "OK") {
        close($sock);
        print "Server gave wrong response to HEARTBEAT: $response\n";
        &tcp_configure();
        return;
    }
    
    print $sock "ENDHEARTBEAT\n";
    $response = <$sock>;
    return if (!defined $response);
    chop $response;
    if (!$response eq "OK") {
        close($sock);
        print "Server gave wrong response to ENDHEARTBEAT: $response\n";
        &tcp_configure();
        return;
    }
    
    close($sock);
    print "^";
    
    return;
}

#-----------------------------------------------------------------------
# write_pid
# Writes the PID (process ID) of this instance to $pidfile.
# This is then used by a seperate script to check (and restart) ihost.
#-----------------------------------------------------------------------
sub write_pid() {
    open PID, ">$pidfile";
    print PID $$;
    close PID;
    
    return;
}
Revision:	1.29
Committed:	Wed Mar 14 18:49:00 2001 UTC (23 years, 8 months ago) by pjm2
Content type:	text/plain
Branch:	MAIN
Changes since 1.28:	+2 -2 lines
Log Message:	Retry time is now ten minutes (wave of arm)
#	Content
1	#!/usr/bin/perl -w
2
3	# -----------------------------------------------------------
4	# Perl i-scream Host.
5	# http://www.i-scream.org.uk
6	#
7	# An all-in-one script to act as an i-scream host on
8	# a typical Unix/Linux box. You may adapt the data-gathering
9	# methods as you see fit.
10	# - pjm2@ukc.ac.uk
11	#
12	# $Author: pjm2 $
13	# $Id: ihost.pl,v 1.28 2001/03/14 18:48:33 pjm2 Exp $
14	#------------------------------------------------------------
15
16	$\| = 1;
17
18	use strict;
19	use IO::Socket;
20	use Sys::Hostname;
21
22	use vars qw (
23	$filter_manager_addr
24	$filter_manager_port
25	$seq_no
26	$udp_update_time
27	$tcp_update_time
28	$last_udp_time
29	$last_tcp_time
30	$last_modified
31	$udp_port
32	$tcp_port
33	$filter_addr
34	$file_list
35	$fqdn
36	$pidfile
37	$retry_wait
38	);
39
40	if (@ARGV != 2) {
41	die "Usage: ihost.pl [i-scream filter manager] [TCP port]\n";
42	}
43
44	$filter_manager_addr = $ARGV[0];
45	$filter_manager_port = $ARGV[1];
46
47	$seq_no = 1;
48	$retry_wait = 600;
49
50	# write our PID to a file
51	$pidfile = "/var/tmp/ihost.pid";
52	&write_pid();
53
54	&tcp_configure();
55	&send_udp_packet();
56
57	$last_udp_time = time;
58	$last_tcp_time = time;
59	while (1) {
60	my($time) = time;
61	if ($time >= $last_udp_time + $udp_update_time) {
62	&send_udp_packet();
63	$last_udp_time = $time;
64	}
65	if ($time >= $last_tcp_time + $tcp_update_time) {
66	&send_tcp_heartbeat();
67	$last_tcp_time = $time;
68	}
69	my($next_udp) = $udp_update_time - $time + $last_udp_time;
70	my($next_tcp) = $tcp_update_time - $time + $last_tcp_time;
71	my($delay);
72	if ($next_udp < $next_tcp) {
73	$delay = $next_udp
74	}
75	else {
76	$delay = $next_tcp;
77	}
78	`sleep $delay`;
79	}
80
81	# we'll probably never get here...
82	`rm -f $pidfile`;
83	exit(0);
84
85
86	#-----------------------------------------------------------------------
87	# wait_then_retry
88	# Waits for the period of time specified in $retry_wait, then attempts
89	# to reconfigure with the server.
90	#-----------------------------------------------------------------------
91	sub wait_then_retry() {
92	print "Will retry configuration with filter manager in $retry_wait seconds.\n";
93	`sleep $retry_wait`;
94	}
95
96
97	#-----------------------------------------------------------------------
98	# tcp_configure
99	# Establishes a TCP connection to the specified i-scream filter manager.
100	# The host then requests details from the server, such as the intervals
101	# at which to send UDP packets.
102	#-----------------------------------------------------------------------
103	sub tcp_configure() {
104
105	while (1 == 1) {
106	my($sock) = new IO::Socket::INET(
107	PeerAddr => $filter_manager_addr,
108	PeerPort => $filter_manager_port,
109	Proto => 'tcp'
110	) or die "Cannot connect!";
111	if (!defined $sock) {
112	print "IHOST ERROR: Could not connect to $filter_manager_addr:$filter_manager_port.\n";
113	print "Please check that there is an i-scream server at this address.\n";
114	close($sock);
115	wait_then_retry();
116	next;
117	}
118
119	# Now run through the configuration process...
120	my($response);
121
122	print $sock "STARTCONFIG\n";
123	$response = <$sock>;
124	if (!chop $response eq "OK") {
125	print "The i-scream server rejected the STARTCONFIG command. Terminated.";
126	close($sock);
127	wait_then_retry();
128	next;
129	}
130
131	print "Config started okay.\n";
132
133	print $sock "LASTMODIFIED\n";
134	$response = <$sock>;
135	chop $response;
136	$last_modified = $response;
137
138	print "Config last modified: ". (scalar localtime $last_modified/1000) . "\n";
139
140	print $sock "FILELIST\n";
141	$response = <$sock>;
142	chop $response;
143	$file_list = $response;
144
145	print "File list obtained: $file_list\n";
146
147	print $sock "FQDN\n";
148	$response = <$sock>;
149	chop $response;
150	$fqdn = $response;
151
152	print "FQDN returned: $fqdn\n";
153
154	print $sock "UDPUpdateTime\n";
155	$response = <$sock>;
156	chop $response;
157	$udp_update_time = $response;
158
159	print $sock "TCPUpdateTime\n";
160	$response = <$sock>;
161	chop $response;
162	$tcp_update_time = $response;
163
164	print "UDP packet period: $udp_update_time seconds.\nTCP heartbeat period: $tcp_update_time seconds.\n";
165
166	print $sock "ENDCONFIG\n";
167	$response = <$sock>;
168	chomp $response;
169	if (!$response eq "OK") {
170	print "ENDCONFIG command to server failed. Terminated.\n";
171	close($sock);
172	wait_then_retry();
173	next;
174	}
175
176	print "Config ended.\n";
177
178	print $sock "FILTER\n";
179	$response = <$sock>;
180	unless (defined($response)) {
181	print "Failed: Could not get a filter address from the filter manager.\n";
182	close($sock);
183	wait_then_retry();
184	next;
185	}
186	chop $response;
187	$response =~ /(.);(.);(.*)/;
188	if ($response eq "ERROR") {
189	print "There are no active configured filters for your host.\n";
190	close($sock);
191	wait_then_retry();
192	next;
193	}
194	($filter_addr, $udp_port, $tcp_port) = ($1, $2, $3);
195	unless (defined($filter_addr) && defined($udp_port) && defined($tcp_port)) {
196	print "Failed: Filter address response from server did not make sense: $response\n";
197	close($sock);
198	wait_then_retry();
199	next;
200	}
201
202	print "Got filter data ($filter_addr, $udp_port, $tcp_port)\n";
203
204	print $sock "END\n";
205	$response = <$sock>;
206	chop $response;
207	if ($response eq "OK") {
208	print "Host successfully configured via TCP.\n"
209	}
210	else {
211	print "The server failed the host configuration on the END command.";
212	close($sock);
213	wait_then_retry();
214	next;
215	}
216
217	close($sock);
218
219	print "Configuration finished sucessfully!\n";
220	last;
221	}
222	return;
223	}
224
225
226
227
228	#-----------------------------------------------------------------------
229	# send_udp_packet
230	# Sends a UDP packet to an i-scream filter.
231	# The packet contains XML markup describing some of the machine's state.
232	# Receipt of UDP packets is not guaranteed.
233	#-----------------------------------------------------------------------
234	sub send_udp_packet() {
235
236	my(@statgrab) = `./statgrab.pl`;
237	my(%packet);
238	for (my($i) = 0; $i <= $#statgrab; $i++) {
239	$statgrab[$i] =~ /^([^\s]) (.)$/;
240	$packet{$1} = $2;
241	}
242
243	my($date) = time;
244
245	my($disk_info) = "<disk>";
246	my($i) = 0;
247	while (defined $packet{"packet.disk.p$i.attributes.mount"}) {
248	$disk_info .= "<p$i";
249	$disk_info .= " name=\"" . $packet{"packet.disk.p$i.attributes.name"} . "\"";
250	$disk_info .= " kbytes=\"" . $packet{"packet.disk.p$i.attributes.kbytes"} . "\"";
251	$disk_info .= " used=\"" . $packet{"packet.disk.p$i.attributes.used"} . "\"";
252	$disk_info .= " avail=\"" . $packet{"packet.disk.p$i.attributes.avail"} . "\"";
253	$disk_info .= " mount=\"" . $packet{"packet.disk.p$i.attributes.mount"} . "\"";
254	$disk_info .= "></p$i>";
255	++$i;
256	}
257	$disk_info .= "</disk>";
258
259	my($ip) = inet_ntoa(scalar(gethostbyname(hostname())) \|\| 'localhost');
260
261	# Build the XML packet this way, as we can clearly
262	# see the structure and contents... I like this ;-)
263	# [Note that the server rejects UDP packets that are
264	# larger than 8196 bytes]
265	my($xml) = <<EOF;
266
267	<packet seq_no="$seq_no" machine_name="$fqdn" date="$date" type="data" ip="$ip">
268	<load>
269	<load1>$packet{"packet.load.load1"}</load1>
270	<load5>$packet{"packet.load.load5"}</load5>
271	<load15>$packet{"packet.load.load15"}</load15>
272	</load>
273	<os>
274	<name>$packet{"packet.os.name"}</name>
275	<release>$packet{"packet.os.release"}</release>
276	<platform>$packet{"packet.os.platform"}</platform>
277	<sysname>$packet{"packet.os.sysname"}</sysname>
278	<version>$packet{"packet.os.version"}</version>
279	<uptime>$packet{"packet.os.uptime"}</uptime>
280	</os>
281	<users>
282	<count>$packet{"packet.users.count"}</count>
283	<list>$packet{"packet.users.list"}</list>
284	</users>
285	<processes>
286	<total>$packet{"packet.processes.total"}</total>
287	<sleeping>$packet{"packet.processes.sleeping"}</sleeping>
288	<zombie>$packet{"packet.processes.zombie"}</zombie>
289	<stopped>$packet{"packet.processes.stopped"}</stopped>
290	<cpu>$packet{"packet.processes.cpu"}</cpu>
291	</processes>
292	<cpu>
293	<idle>$packet{"packet.cpu.idle"}</idle>
294	<user>$packet{"packet.cpu.user"}</user>
295	<kernel>$packet{"packet.cpu.kernel"}</kernel>
296	<iowait>$packet{"packet.cpu.iowait"}</iowait>
297	<swap>$packet{"packet.cpu.swap"}</swap>
298	</cpu>
299	<memory>
300	<total>$packet{"packet.memory.total"}</total>
301	<free>$packet{"packet.memory.free"}</free>
302	</memory>
303	<swap>
304	<total>$packet{"packet.swap.total"}</total>
305	<free>$packet{"packet.swap.free"}</free>
306	</swap>
307	$disk_info
308	</packet>
309
310	EOF
311
312	# Make the packet smaller by stripping out newlines and leading spaces.
313	$xml =~ s/\n\s*//g;
314
315	my($sock) = new IO::Socket::INET (
316	PeerPort => $udp_port,
317	PeerAddr => $filter_addr,
318	Proto => 'udp'
319	) or die "Could not send UDP: $!\n";
320
321	print $sock $xml or die "Could not send UDP packet: $!\n";
322	close($sock);
323	$seq_no++;
324	print "-";
325
326	return;
327	}
328
329
330
331
332	#-----------------------------------------------------------------------
333	# send_tcp_heartbeat
334	# Establishes a TCP connection to an i-scream filter.
335	# The heartbeat is used as a guaranteed "I'm alive" delivery mechanism.
336	#-----------------------------------------------------------------------
337	sub send_tcp_heartbeat() {
338
339	my($sock) = new IO::Socket::INET(
340	PeerAddr => $filter_addr,
341	PeerPort => $tcp_port,
342	Proto => 'tcp'
343	) or return;
344	if (!defined $sock) {
345	print "IHOST WARNING: Failed to deliver a heartbeat to the i-scream filter.\n";
346	&tcp_configure();
347	return;
348	}
349
350	# Now run through the configuration process.
351	my($response);
352
353	print $sock "HEARTBEAT\n";
354	$response = <$sock>;
355	return if (!defined $response);
356	chop $response;
357	if (!$response eq "OK") {
358	close($sock);
359	print "Server gave wrong response to HEARTBEAT: $response\n";
360	&tcp_configure();
361	return;
362	}
363
364	print $sock "CONFIG\n";
365	$response = <$sock>;
366	return if (!defined $response);
367	chop $response;
368	if (!$response eq "OK") {
369	close($sock);
370	print "Server gave wrong response to CONFIG: $response\n";
371	&tcp_configure();
372	return;
373	}
374
375	print $sock "$file_list\n";
376	$response = <$sock>;
377	return if (!defined $response);
378	chop $response;
379	if (!$response eq "OK") {
380	close($sock);
381	print "Server gave wrong response to file list: $response\n";
382	&tcp_configure();
383	return;
384	}
385
386	print $sock "$last_modified\n";
387	$response = <$sock>;
388	return if (!defined $response);
389	chop $response;
390	if ($response eq "ERROR") {
391	close($sock);
392	print "Server configuration changed. Reconfiguring with filter manager.\n";
393	&tcp_configure();
394	return;
395	}
396	if (!$response eq "OK") {
397	close($sock);
398	print "Server gave wrong response to HEARTBEAT: $response\n";
399	&tcp_configure();
400	return;
401	}
402
403	print $sock "ENDHEARTBEAT\n";
404	$response = <$sock>;
405	return if (!defined $response);
406	chop $response;
407	if (!$response eq "OK") {
408	close($sock);
409	print "Server gave wrong response to ENDHEARTBEAT: $response\n";
410	&tcp_configure();
411	return;
412	}
413
414	close($sock);
415	print "^";
416
417	return;
418	}
419
420	#-----------------------------------------------------------------------
421	# write_pid
422	# Writes the PID (process ID) of this instance to $pidfile.
423	# This is then used by a seperate script to check (and restart) ihost.
424	#-----------------------------------------------------------------------
425	sub write_pid() {
426	open PID, ">$pidfile";
427	print PID $$;
428	close PID;
429
430	return;
431	}