1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
|
NAME
Net::Ping - check a remote host for reachability
$Id: Ping.pm,v 1.16 2002/01/05 23:36:54 rob Exp $
SYNOPSIS
use Net::Ping;
$p = Net::Ping->new();
print "$host is alive.\n" if $p->ping($host);
$p->close();
$p = Net::Ping->new("icmp");
$p->bind($my_addr); # Specify source interface of pings
foreach $host (@host_array)
{
print "$host is ";
print "NOT " unless $p->ping($host, 2);
print "reachable.\n";
sleep(1);
}
$p->close();
$p = Net::Ping->new("tcp", 2);
# Try connecting to the www port instead of the echo port
$p->{port_num} = getservbyname("http", "tcp");
while ($stop_time > time())
{
print "$host not reachable ", scalar(localtime()), "\n"
unless $p->ping($host);
sleep(300);
}
undef($p);
# For backward compatibility
print "$host is alive.\n" if pingecho($host);
DESCRIPTION
This module contains methods to test the reachability of remote hosts on
a network. A ping object is first created with optional parameters, a
variable number of hosts may be pinged multiple times and then the
connection is closed.
You may choose one of four different protocols to use for the ping. The
"udp" protocol is the default. Note that a live remote host may still
fail to be pingable by one or more of these protocols. For example,
www.microsoft.com is generally alive but not pingable.
With the "tcp" protocol the ping() method attempts to establish a
connection to the remote host's echo port. If the connection is
successfully established, the remote host is considered reachable. No
data is actually echoed. This protocol does not require any special
privileges but has higher overhead than the other two protocols.
Specifying the "udp" protocol causes the ping() method to send a udp
packet to the remote host's echo port. If the echoed packet is received
from the remote host and the received packet contains the same data as
the packet that was sent, the remote host is considered reachable. This
protocol does not require any special privileges. It should be borne in
mind that, for a udp ping, a host will be reported as unreachable if it
is not running the appropriate echo service. For Unix-like systems see
the inetd(8) manpage for more information.
If the "icmp" protocol is specified, the ping() method sends an icmp
echo message to the remote host, which is what the UNIX ping program
does. If the echoed message is received from the remote host and the
echoed information is correct, the remote host is considered reachable.
Specifying the "icmp" protocol requires that the program be run as root
or that the program be setuid to root.
If the "external" protocol is specified, the ping() method attempts to
use the `Net::Ping::External' module to ping the remote host.
`Net::Ping::External' interfaces with your system's default `ping'
utility to perform the ping, and generally produces relatively accurate
results. If `Net::Ping::External' if not installed on your system,
specifying the "external" protocol will result in an error.
Functions
Net::Ping->new([$proto [, $def_timeout [, $bytes]]]);
Create a new ping object. All of the parameters are optional. $proto
specifies the protocol to use when doing a ping. The current choices
are "tcp", "udp" or "icmp". The default is "udp".
If a default timeout ($def_timeout) in seconds is provided, it is
used when a timeout is not given to the ping() method (below). The
timeout must be greater than 0 and the default, if not specified, is
5 seconds.
If the number of data bytes ($bytes) is given, that many data bytes
are included in the ping packet sent to the remote host. The number
of data bytes is ignored if the protocol is "tcp". The minimum (and
default) number of data bytes is 1 if the protocol is "udp" and 0
otherwise. The maximum number of data bytes that can be specified is
1024.
$p->bind($local_addr);
Sets the source address from which pings will be sent. This must be
the address of one of the interfaces on the local host. $local_addr
may be specified as a hostname or as a text IP address such as
"192.168.1.1".
If the protocol is set to "tcp", this method may be called any
number of times, and each call to the ping() method (below) will use
the most recent $local_addr. If the protocol is "icmp" or "udp",
then bind() must be called at most once per object, and (if it is
called at all) must be called before the first call to ping() for
that object.
$p->ping($host [, $timeout]);
Ping the remote host and wait for a response. $host can be either
the hostname or the IP number of the remote host. The optional
timeout must be greater than 0 seconds and defaults to whatever was
specified when the ping object was created. If the hostname cannot
be found or there is a problem with the IP number, undef is
returned. Otherwise, 1 is returned if the host is reachable and 0 if
it is not. For all practical purposes, undef and 0 and can be
treated as the same case.
$p->open($host);
When you are using the stream protocol, this call pre-opens the tcp
socket. It's only necessary to do this if you want to provide a
different timeout when creating the connection, or remove the
overhead of establishing the connection from the first ping. If you
don't call `open()', the connection is automatically opened the
first time `ping()' is called. This call simply does nothing if you
are using any protocol other than stream.
$p->open($host);
When you are using the stream protocol, this call pre-opens the tcp
socket. It's only necessary to do this if you want to provide a
different timeout when creating the connection, or remove the
overhead of establishing the connection from the first ping. If you
don't call `open()', the connection is automatically opened the
first time `ping()' is called. This call simply does nothing if you
are using any protocol other than stream.
$p->close();
Close the network connection for this ping object. The network
connection is also closed by "undef $p". The network connection is
automatically closed if the ping object goes out of scope (e.g. $p
is local to a subroutine and you leave the subroutine).
pingecho($host [, $timeout]);
To provide backward compatibility with the previous version of
Net::Ping, a pingecho() subroutine is available with the same
functionality as before. pingecho() uses the tcp protocol. The
return values and parameters are the same as described for the
ping() method. This subroutine is obsolete and may be removed in a
future version of Net::Ping.
WARNING
pingecho() or a ping object with the tcp protocol use alarm() to
implement the timeout. So, don't use alarm() in your program while you
are using pingecho() or a ping object with the tcp protocol. The udp and
icmp protocols do not use alarm() to implement the timeout.
NOTES
There will be less network overhead (and some efficiency in your
program) if you specify either the udp or the icmp protocol. The tcp
protocol will generate 2.5 times or more traffic for each ping than
either udp or icmp. If many hosts are pinged frequently, you may wish to
implement a small wait (e.g. 25ms or more) between each ping to avoid
flooding your network with packets.
The icmp protocol requires that the program be run as root or that it be
setuid to root. The other protocols do not require special privileges,
but not all network devices implement tcp or udp echo.
Local hosts should normally respond to pings within milliseconds.
However, on a very congested network it may take up to 3 seconds or
longer to receive an echo packet from the remote host. If the timeout is
set too low under these conditions, it will appear that the remote host
is not reachable (which is almost the truth).
Reachability doesn't necessarily mean that the remote host is actually
functioning beyond its ability to echo packets. tcp is slightly better
at indicating the health of a system than icmp because it uses more of
the networking stack to respond.
Because of a lack of anything better, this module uses its own routines
to pack and unpack ICMP packets. It would be better for a separate
module to be written which understands all of the different kinds of
ICMP packets.
AUTHORS
Current maintainers:
colinm@cpan.org (Colin McMillen)
bbb@cpan.org (Rob Brown)
Stream protocol:
bronson@trestle.com (Scott Bronson)
Original pingecho():
karrer@bernina.ethz.ch (Andreas Karrer)
pmarquess@bfsec.bt.co.uk (Paul Marquess)
Original Net::Ping author:
mose@ns.ccsn.edu (Russell Mosemann)
COPYRIGHT
Copyright (c) 2001, Colin McMillen. All rights reserved.
Copyright (c) 2001, Rob Brown. All rights reserved.
This program is free software; you may redistribute it and/or modify it
under the same terms as Perl itself.
|
