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Team-Fly®
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Linux Socket Programming by Example
Warren W. Gay
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Linux Socket Programming by Example
Copyright © 2000 by Que®
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assumed for damages resulting from the use of the information contained herein.
International Standard Book Numbe-r7: 8097-2241-0
Library of Congress Catalog Card Numb-e6r6:4 5949
Printed in the United States of America
First Printing: April 2000
02 01 00 4 3 2 1
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Page iii
CONTENTS AT A GLANCE
Introduction 1
Part 1: Basic Socket Concepts 5
1 7
Introducing Sockets
2 35
Domains and Address Families
3 65
Address Conversion Functions
4 93
Socket Types and Protocols
5 115
Binding Addresses to a Socket
6 133
Connectionless-Oriented Protocols
7 159
Connection-Oriented Protocols for Clients
8 183
Connection-Oriented Protocols for Servers
9 203
Hostname and Network Name Lookups
Part 2: Advanced Socket Programming 227
10 229
Using Standard I/O on Sockets
11 269
Concurrent Client Servers
12 305
Socket Options
329
13
Broadcasting with UDP
14 349
Out-of-Band Data
15 379
Using the inetd Daemon
16 393
Network Security Programming
17 427
Passing Credentials and File Descriptors
18 473
A Practical Network Project
Appendixes 505
A 507
Socket Function Quick Reference
B 519
Socket-Related Structures Reference
C 525
Useful Network Tables
Glossary 529
Index 537
Page iv
TABLE OF CONTENTS
Introduction 1
Part 1 5
Basic Socket Concepts
1 7
Introducing Sockets
A Brief Historical Introduction 8
Understanding Sockets 9
Defining a Socket 9
Using Sockets 10
Referencing Sockets 11
Comparing Sockets to Pipes 12
Creating Sockets 13
Using socketpair(2) in an Example 14
Running the Demonstration Program 16
Performing I/O on Sockets 17
Closing Sockets 21
The shutdown(2) Function 22
Shutting Down Writing to a Socket 22
Dealing with Duplicated Sockets 23
Shutting Down Reading from a Socket 24
Knowing When Not to Use shutdown(2) 24
Writing a Client/Server Example 24
2 35
Domains and Address Families
Nameless Sockets 36
Anonymous Calls 36
Generating Addresses 36
Understanding Domains 36
Forming Socket Addresses 37
Examining the Generic Socket Address 37
Forming Local Addresses 38
Forming Traditional Local Addresses 39
Forming Abstract Local Addresses 44
Forming Internet (IPv4) Socket Addresses 47
Understanding Network Byte Order 49
Performing Endian Conversions 50
Page v
Initializing a Wild Internet Address 51
Initializing a Specific Internet Address 52
Specifying an X.25 Address 55
Specifying Other Address Families 58
The AF_UNSPEC Address Family 61
3 65
Address Conversion Functions
Internet IP Numbers 66
Internet Address Classes 66
Understanding Netmask Values 67
Allocating IP Addresses 72
Private IP Numbers 72
Reserved IP Numbers 73
Manipulating IP Numbers 73
Using the inet_addr(3) Function 73
The inet_aton(3) Function 77
Using the inet_ntoa(3) Function 80
Using inet_network(3) 83
Using the inet_lnaof(3) Function 85
Using the inet_netof(3) Function 86
Using the inet_makeaddr(3) Function 87
4 93
Socket Types and Protocols
Specifying the Domain of a Socket 94
Choosing PF_INET or AF_INET 94
Using the PF_LOCAL and AF_LOCAL Macros 95
Using the socket(2) Function 96
Choosing a Socket Type 96
Understanding the SOCK_STREAM Socket 97
Type
Understanding the SOCK_DGRAM Socket Type 99
Understanding the SOCK_SEQPACKET Socket Type 100
Choosing a Protocol 101
Using PF_LOCAL and SOCK_STREAM 102
Using PF_LOCAL and SOCK_DGRAM 103
Using PF_INET and SOCK_STREAM 103
Using PF_INET and SOCK_DGRAM 105
Socket Domain and Type Summary 106
Other Linux-Supported Protocols 107
Researching Other Protocols 109
