HP Rp3440-4 - 9000 - 0 MB RAM Manual

BSD Sockets Interface Programmer’s
Guide
Edition 6
B2355-90136
HP 9000 Networking
E0497
Printed in: United States
© Copyright 1997 Hewlett-Packard Company.

2
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3
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Contents
5
1. BSD Sockets Concepts
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Key Terms and Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
How You Can Use BSD Sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
The Client-Server Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Creating a Connection: the Client-Server Model . . . . . . . . . . . . . . . . .21
BSD Sockets Library Routines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
2. Using Internet Stream Sockets
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
Preparing Address Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Declaring Socket Address Variables . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Getting the Remote Host's Internet Address . . . . . . . . . . . . . . . . . . . .32
Getting the Port Address for the Desired Service . . . . . . . . . . . . . . . .33
Using a Wildcard Local Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Writing the Server Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
Creating a Socket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
Binding a Socket Address to the Server Process's Socket . . . . . . . . . .36
Setting Up the Server to Wait for Connection Requests . . . . . . . . . . .37
Accepting a Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
Writing the Client Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Creating a Socket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Requesting a Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
Sending and Receiving Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Sending Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Receiving Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
Flag Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
Closing a Socket. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47

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Contents
Example Using Internet Stream Sockets . . . . . . . . . . . . . . . . . . . . . . . . 48
3. Advanced Topics for Stream Sockets
Socket Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Getting and Setting Socket Options. . . . . . . . . . . . . . . . . . . . . . . . . . . 62
SO_REUSEADDR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
SO_KEEPALIVE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
SO_DONTROUTE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
SO_SNDBUF. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
SO_RCVBUF. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
SO_LINGER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
SO_USELOOPBACK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
SO_OOBINLINE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
SO_SNDLOWAT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
SO_RCVLOWAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
SO_SNDTIMEO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
SO_RCVTIMEO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
SO_TYPE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
SO_ERROR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
SO_BROADCAST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
SO_REUSEPORT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Synchronous I/O Multiplexing with Select. . . . . . . . . . . . . . . . . . . . . . . 72
Sending and Receiving Data Asynchronously . . . . . . . . . . . . . . . . . . . . 75
Nonblocking I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Using Shutdown. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
When to Shut Down a Socket. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Using Read and Write to Make Stream Sockets Transparent . . . . . . . 80
Sending and Receiving Out-of-band Data. . . . . . . . . . . . . . . . . . . . . . . . 81

Contents
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4. Using Internet Datagram Sockets
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86
Preparing Address Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .88
Declaring Socket Address Variables . . . . . . . . . . . . . . . . . . . . . . . . . . .88
Getting the Remote Host's Network Address. . . . . . . . . . . . . . . . . . . .89
Getting the Port Address for the Desired Service . . . . . . . . . . . . . . . .90
Using a Wildcard Local Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91
Writing the Server and Client Processes . . . . . . . . . . . . . . . . . . . . . . . . .92
Creating Sockets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92
Binding Socket Addresses to Datagram Sockets . . . . . . . . . . . . . . . . .93
Sending and Receiving Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95
Sending Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95
Receiving Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96
Flag Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98
Closing a Socket. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100
Example Using Datagram Sockets. . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
5. Advanced Topics for Internet Datagram Sockets
SO_BROADCAST Socket Option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .111
Specifying a Default Socket Address . . . . . . . . . . . . . . . . . . . . . . . . . . .112
When to Specify a Default Socket Address. . . . . . . . . . . . . . . . . . . . .113
Synchronous I/O Multiplexing with Select. . . . . . . . . . . . . . . . . . . . . . .114
Sending and Receiving Data Asynchronously . . . . . . . . . . . . . . . . . . . .115
Sending and Receiving IP Multicast Datagrams. . . . . . . . . . . . . . . . . .116
Sending IP Multicast Datagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . .116
Receiving IP Multicast Datagrams . . . . . . . . . . . . . . . . . . . . . . . . . . .118
Nonblocking I/O. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121

8
Contents
Using Broadcast Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
6. Using UNIX Domain Stream Sockets
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
Preparing Address Variables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
Declaring Socket Address Variables . . . . . . . . . . . . . . . . . . . . . . . . . 126
Writing the Server Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
Creating a Socket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
Binding a Socket Address to the Server Process's Socket . . . . . . . . 129
Setting the Server Up to Wait for Connection Requests. . . . . . . . . . 130
Accepting a Connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
Writing the Client Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
Creating a Socket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
Requesting a Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
Sending and Receiving Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
Sending Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
Receiving Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
Flag Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
Closing a Socket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
Example Using UNIX Domain Stream Sockets . . . . . . . . . . . . . . . . . . 140
7. Using UNIX Domain Datagram Sockets
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
Preparing Address Variables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Declaring Socket Address Variables . . . . . . . . . . . . . . . . . . . . . . . . . 150
Writing the Server and Client Processes . . . . . . . . . . . . . . . . . . . . . . . 152
Creating Sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
Binding Socket Addresses to UNIX Domain Datagram Sockets . . . 153

Contents
9
Sending and Receiving Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .155
Sending Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .155
Receiving Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .156
Closing a Socket. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .159
Example Using UNIX Domain Datagram Sockets . . . . . . . . . . . . . . . .160
8. Programming Hints
Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167
Using Diagnostic Utilities as Troubleshooting Tools. . . . . . . . . . . . . . .168
Adding a Server Process to the Internet Daemon . . . . . . . . . . . . . . . . .169
Summary Tables for System and Library Calls. . . . . . . . . . . . . . . . . . .173
Portability Issues. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177
Porting Issues for IPC Functions and Library Calls . . . . . . . . . . . . .177
Porting Issues for Other Functions and Library Calls Typically Used by
IPC178
A. BSD Sockets Quick Reference Table
Quick Reference Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182
Glossary

10
Contents