Programming the Network with Perl - Wiley 2002.pdf

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155126534 UNPDF
Paul Barry
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Copyright ©2002 John Wiley & Sons Ltd
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Library of Congress Cataloging-in-Publication Data
(applied for)
British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library
ISBN 0 471 48670 1
Typeset in 9.5/12.5pt Lucida Bright by T & T Productions Ltd, London.
Printed and bound in Great Britain by Biddles Ltd, Guildford and Kings Lynn.
This book is printed on acid-free paper responsibly manufactured from sustainable
forestry in which at least two trees are planted for each one used for paper production.
Dedicated to Deirdre,
for continuing to put her ambitions on hold
while I pursue mine.
Contents
Preface
xiii
1 Meet Perl
1
1.1
Perl’s Default Behaviour
1
1.1.1
Our first Perl program
2
1.1.2
Perl’s default variable
3
1.1.3
The strange first line explained
3
1.2
Using Variables in Perl
4
1.2.1
One of something: scalars
5
1.2.2
A collection of somethings: arrays and lists
6
1.2.3
Hashes
8
1.2.4
References
9
1.2.5
Built-in variables
12
1.2.6
Scoping with local , my and our
12
1.3
Controlling Flow
13
1.3.1 if
13
1.3.2
The ternary conditional operator
14
1.3.3 while
15
1.3.4 for
15
1.3.5 unless
16
1.3.6 until
16
1.3.7 foreach
16
1.3.8 do
17
1.3.9 eval
17
1.3.10 Statement modifiers
18
1.4
Boolean in Perl
19
1.5
Perl Operators
20
1.6
Subroutines
21
1.6.1
Processing parameters
21
1.6.2
Returning results
22
1.6.3
I want an array
23
1.6.4
In-built subroutines
23
1.6.5
References to subroutines
26
1.7
Perl I/O
26
1.7.1
Variable interpolation
28
1.8
Packages, Modules and Objects
29
1.8.1
Modules
30
1.8.2
Objects
30
1.8.3
The joy of CPAN
31
1.9
More Perl
32
1.10 Where To From Here?
32
viii Contents
1.11 Print Resources
32
1.12 Web Resources
33
2 Snooping
35
2.1
Thank You, Tim Potter
36
2.2
Preparing To Snoop
37
2.2.1
Installing NetPacket::*
37
2.2.2
Installing Net::Pcap
38
2.2.3
Installing Net::PcapUtils
39
2.2.4
Online documentation
39
2.2.5
Configuring your network interface
40
2.3
Building Low-Level Snooping Tools
41
2.3.1 loop
=
open
+
next
42
2.3.2
Optional parameters: loop and open
43
2.3.3
Optional parameters: the callback function
45
2.3.4
Ethernet Analysis
45
2.3.5
EtherSnooper (v0.01)
48
2.3.6
EtherSnooper (v0.02)
52
2.3.7
EtherSnooper (v0.03)
55
2.3.8
Displaying IP addresses
58
2.4
Snooping IP Datagrams
63
2.4.1
EtherSnooper (v0.05)
64
2.4.2
EtherSnooper (v0.06)
67
2.5
Transport Snoopers
69
2.5.1
Preparing to snoop UDP
70
2.5.2
Preparing to snoop TCP
70
2.5.3
The TCP and UDP gotcha!
71
2.5.4
Application trac monitoring
75
2.5.5
EtherSnooper (v0.07)
81
2.6
The Network Debugger
83
2.6.1
Processing command-line parameters
85
2.6.2
Storing captured results
85
2.6.3
The NetDebug source code
86
2.7
Where To From Here?
95
2.8
Print Resources
95
2.9
Web Resources
96
3 Sockets
99
3.1
Clients and Servers
99
3.1.1
Client characteristics
100
3.1.2
Server characteristics
101
3.2
Transport Services
101
3.2.1
Unreliable transport
102
3.2.2
Reliable transport
103
3.3
Introducing the Perl Socket API
104
3.4
Socket Support Subroutines
105
3.4.1 inet_aton and inet_ntoa
105
3.4.2
Socket addresses
105
3.4.3 getservbyname and getservbyport
106
3.4.4 getprotobyname and getprotobynumber
106
3.4.5 gethostbyname and gethostbyaddr
107
3.5
Simple UDP Clients and Servers
108
3.5.1
Testing with localhost
108
3.5.2
The first UDP server
108
3.5.3
The first UDP client
111

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