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 1.29 2001/03/14 18:49:00 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";
            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:	1.30
Committed:	Thu Mar 15 09:44:08 2001 UTC (23 years, 8 months ago) by pjm2
Content type:	text/plain
Branch:	MAIN
Changes since 1.29:	+1 -2 lines
Log Message:	If we cannot connect to the filter manager, then we shall retry without closing the socket, as it won't be open to close ;)
#	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 1.29 2001/03/14 18:49:00 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	wait_then_retry();
115	next;
116	}
117
118	# Now run through the configuration process...
119	my($response);
120
121	print $sock "STARTCONFIG\n";
122	$response = <$sock>;
123	if (!chop $response eq "OK") {
124	print "The i-scream server rejected the STARTCONFIG command. Terminated.";
125	close($sock);
126	wait_then_retry();
127	next;
128	}
129
130	print "Config started okay.\n";
131
132	print $sock "LASTMODIFIED\n";
133	$response = <$sock>;
134	chop $response;
135	$last_modified = $response;
136
137	print "Config last modified: ". (scalar localtime $last_modified/1000) . "\n";
138
139	print $sock "FILELIST\n";
140	$response = <$sock>;
141	chop $response;
142	$file_list = $response;
143
144	print "File list obtained: $file_list\n";
145
146	print $sock "FQDN\n";
147	$response = <$sock>;
148	chop $response;
149	$fqdn = $response;
150
151	print "FQDN returned: $fqdn\n";
152
153	print $sock "UDPUpdateTime\n";
154	$response = <$sock>;
155	chop $response;
156	$udp_update_time = $response;
157
158	print $sock "TCPUpdateTime\n";
159	$response = <$sock>;
160	chop $response;
161	$tcp_update_time = $response;
162
163	print "UDP packet period: $udp_update_time seconds.\nTCP heartbeat period: $tcp_update_time seconds.\n";
164
165	print $sock "ENDCONFIG\n";
166	$response = <$sock>;
167	chomp $response;
168	if (!$response eq "OK") {
169	print "ENDCONFIG command to server failed. Terminated.\n";
170	close($sock);
171	wait_then_retry();
172	next;
173	}
174
175	print "Config ended.\n";
176
177	print $sock "FILTER\n";
178	$response = <$sock>;
179	unless (defined($response)) {
180	print "Failed: Could not get a filter address from the filter manager.\n";
181	close($sock);
182	wait_then_retry();
183	next;
184	}
185	chop $response;
186	$response =~ /(.);(.);(.*)/;
187	if ($response eq "ERROR") {
188	print "There are no active configured filters for your host.\n";
189	close($sock);
190	wait_then_retry();
191	next;
192	}
193	($filter_addr, $udp_port, $tcp_port) = ($1, $2, $3);
194	unless (defined($filter_addr) && defined($udp_port) && defined($tcp_port)) {
195	print "Failed: Filter address response from server did not make sense: $response\n";
196	close($sock);
197	wait_then_retry();
198	next;
199	}
200
201	print "Got filter data ($filter_addr, $udp_port, $tcp_port)\n";
202
203	print $sock "END\n";
204	$response = <$sock>;
205	chop $response;
206	if ($response eq "OK") {
207	print "Host successfully configured via TCP.\n"
208	}
209	else {
210	print "The server failed the host configuration on the END command.";
211	close($sock);
212	wait_then_retry();
213	next;
214	}
215
216	close($sock);
217
218	print "Configuration finished sucessfully!\n";
219	last;
220	}
221	return;
222	}
223
224
225
226
227	#-----------------------------------------------------------------------
228	# send_udp_packet
229	# Sends a UDP packet to an i-scream filter.
230	# The packet contains XML markup describing some of the machine's state.
231	# Receipt of UDP packets is not guaranteed.
232	#-----------------------------------------------------------------------
233	sub send_udp_packet() {
234
235	my(@statgrab) = `./statgrab.pl`;
236	my(%packet);
237	for (my($i) = 0; $i <= $#statgrab; $i++) {
238	$statgrab[$i] =~ /^([^\s]) (.)$/;
239	$packet{$1} = $2;
240	}
241
242	my($date) = time;
243
244	my($disk_info) = "<disk>";
245	my($i) = 0;
246	while (defined $packet{"packet.disk.p$i.attributes.mount"}) {
247	$disk_info .= "<p$i";
248	$disk_info .= " name=\"" . $packet{"packet.disk.p$i.attributes.name"} . "\"";
249	$disk_info .= " kbytes=\"" . $packet{"packet.disk.p$i.attributes.kbytes"} . "\"";
250	$disk_info .= " used=\"" . $packet{"packet.disk.p$i.attributes.used"} . "\"";
251	$disk_info .= " avail=\"" . $packet{"packet.disk.p$i.attributes.avail"} . "\"";
252	$disk_info .= " mount=\"" . $packet{"packet.disk.p$i.attributes.mount"} . "\"";
253	$disk_info .= "></p$i>";
254	++$i;
255	}
256	$disk_info .= "</disk>";
257
258	my($ip) = inet_ntoa(scalar(gethostbyname(hostname())) \|\| 'localhost');
259
260	# Build the XML packet this way, as we can clearly
261	# see the structure and contents... I like this ;-)
262	# [Note that the server rejects UDP packets that are
263	# larger than 8196 bytes]
264	my($xml) = <<EOF;
265
266	<packet seq_no="$seq_no" machine_name="$fqdn" date="$date" type="data" ip="$ip">
267	<load>
268	<load1>$packet{"packet.load.load1"}</load1>
269	<load5>$packet{"packet.load.load5"}</load5>
270	<load15>$packet{"packet.load.load15"}</load15>
271	</load>
272	<os>
273	<name>$packet{"packet.os.name"}</name>
274	<release>$packet{"packet.os.release"}</release>
275	<platform>$packet{"packet.os.platform"}</platform>
276	<sysname>$packet{"packet.os.sysname"}</sysname>
277	<version>$packet{"packet.os.version"}</version>
278	<uptime>$packet{"packet.os.uptime"}</uptime>
279	</os>
280	<users>
281	<count>$packet{"packet.users.count"}</count>
282	<list>$packet{"packet.users.list"}</list>
283	</users>
284	<processes>
285	<total>$packet{"packet.processes.total"}</total>
286	<sleeping>$packet{"packet.processes.sleeping"}</sleeping>
287	<zombie>$packet{"packet.processes.zombie"}</zombie>
288	<stopped>$packet{"packet.processes.stopped"}</stopped>
289	<cpu>$packet{"packet.processes.cpu"}</cpu>
290	</processes>
291	<cpu>
292	<idle>$packet{"packet.cpu.idle"}</idle>
293	<user>$packet{"packet.cpu.user"}</user>
294	<kernel>$packet{"packet.cpu.kernel"}</kernel>
295	<iowait>$packet{"packet.cpu.iowait"}</iowait>
296	<swap>$packet{"packet.cpu.swap"}</swap>
297	</cpu>
298	<memory>
299	<total>$packet{"packet.memory.total"}</total>
300	<free>$packet{"packet.memory.free"}</free>
301	</memory>
302	<swap>
303	<total>$packet{"packet.swap.total"}</total>
304	<free>$packet{"packet.swap.free"}</free>
305	</swap>
306	$disk_info
307	</packet>
308
309	EOF
310
311	# Make the packet smaller by stripping out newlines and leading spaces.
312	$xml =~ s/\n\s*//g;
313
314	my($sock) = new IO::Socket::INET (
315	PeerPort => $udp_port,
316	PeerAddr => $filter_addr,
317	Proto => 'udp'
318	) or die "Could not send UDP: $!\n";
319
320	print $sock $xml or die "Could not send UDP packet: $!\n";
321	close($sock);
322	$seq_no++;
323	print "-";
324
325	return;
326	}
327
328
329
330
331	#-----------------------------------------------------------------------
332	# send_tcp_heartbeat
333	# Establishes a TCP connection to an i-scream filter.
334	# The heartbeat is used as a guaranteed "I'm alive" delivery mechanism.
335	#-----------------------------------------------------------------------
336	sub send_tcp_heartbeat() {
337
338	my($sock) = new IO::Socket::INET(
339	PeerAddr => $filter_addr,
340	PeerPort => $tcp_port,
341	Proto => 'tcp'
342	) or return;
343	if (!defined $sock) {
344	print "IHOST WARNING: Failed to deliver a heartbeat to the i-scream filter.\n";
345	&tcp_configure();
346	return;
347	}
348
349	# Now run through the configuration process.
350	my($response);
351
352	print $sock "HEARTBEAT\n";
353	$response = <$sock>;
354	return if (!defined $response);
355	chop $response;
356	if (!$response eq "OK") {
357	close($sock);
358	print "Server gave wrong response to HEARTBEAT: $response\n";
359	&tcp_configure();
360	return;
361	}
362
363	print $sock "CONFIG\n";
364	$response = <$sock>;
365	return if (!defined $response);
366	chop $response;
367	if (!$response eq "OK") {
368	close($sock);
369	print "Server gave wrong response to CONFIG: $response\n";
370	&tcp_configure();
371	return;
372	}
373
374	print $sock "$file_list\n";
375	$response = <$sock>;
376	return if (!defined $response);
377	chop $response;
378	if (!$response eq "OK") {
379	close($sock);
380	print "Server gave wrong response to file list: $response\n";
381	&tcp_configure();
382	return;
383	}
384
385	print $sock "$last_modified\n";
386	$response = <$sock>;
387	return if (!defined $response);
388	chop $response;
389	if ($response eq "ERROR") {
390	close($sock);
391	print "Server configuration changed. Reconfiguring with filter manager.\n";
392	&tcp_configure();
393	return;
394	}
395	if (!$response eq "OK") {
396	close($sock);
397	print "Server gave wrong response to HEARTBEAT: $response\n";
398	&tcp_configure();
399	return;
400	}
401
402	print $sock "ENDHEARTBEAT\n";
403	$response = <$sock>;
404	return if (!defined $response);
405	chop $response;
406	if (!$response eq "OK") {
407	close($sock);
408	print "Server gave wrong response to ENDHEARTBEAT: $response\n";
409	&tcp_configure();
410	return;
411	}
412
413	close($sock);
414	print "^";
415
416	return;
417	}
418
419	#-----------------------------------------------------------------------
420	# write_pid
421	# Writes the PID (process ID) of this instance to $pidfile.
422	# This is then used by a seperate script to check (and restart) ihost.
423	#-----------------------------------------------------------------------
424	sub write_pid() {
425	open PID, ">$pidfile";
426	print PID $$;
427	close PID;
428
429	return;
430	}