Visual Basic 6.0 Internet Programming

406 Pages·1999·3.54 MB·English

by  Carl Franklin

To access the contents, click the chapter and section titles.
Visual Basic 6.0 Internet Programming
(Publisher: John Wiley & Sons, Inc.)
Author(s): Carl Franklin
ISBN: 0471314986
Publication Date: 02/01/99

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FOREWORD
CHAPTER 1—THE INTERNET
Attack of the Buzzwords!
Protocols and Data
Protocol Stacks and the OSI Model
TCP/IP
Names and Addresses
Ports
Name Resolution
Sockets
The TCP/IP Model
CHAPTER 2—WINSOCK PROGRAMMING
Introduction
Why Not Use the Winsock API?
Installing the Software
Loading DSSOCK32.OCX into Visual Basic
DSSOCK.BAS
SocketConnect
IsDotAddress
ParseString
Getting Started with dsSocket
Making a Sockets Connection
What’s Going On Here?
SocketID and the Socket Property
Closing the Connection
Handling Multiple Connections on the Server Side
Sending Data
Receiving Data
LineMode, EOLChar, and DataSize
The Simple Approach
A New Twist
Splitting Up the Process with Flags
A Slight Variation
Event Driven = No Loops
Which Approach Is Better?
Error Handling
Winsock Errors
Error-Handling Techniques
Minimal Error Trapping
Debug.Print Error Trapping
Message Dialog Reporting
Error Log Reporting
UDP—User Datagram Protocol
Terminal—A Winsock Terminal Program
Epilogue
CHAPTER 3—SIMPLE PROTOCOLS
Introduction
NTP (Network Time Protocol)
WHOIS
FINGER
SetTime Application
Epilogue
CHAPTER 4—USENET NEWS
Introduction
NNTP
MessageIDs vs. Message Numbers
NNTP Versions
NNTP Commands
Sample Conversation
The WILDMAT Format
Server Responses
Usenet Article Format
VB Programming Technique
String Parsing
The szParseString Function
Sample Program—NNTP.VBP
Connecting to an NNTP Server
Retrieving an Article Header
Retrieving a Complete Article
Retrieving Article Information
Example: Displaying Article Descriptions in a
List Box
Posting an Article
Posting a Reply to a Previous Message
Retrieving a List of Newsgroups
LIST ACTIVE Returns Selective Newsgroups
XGTITLE Returns Newsgroup Descriptions
LIST NEWSGROUPS also Returns Newsgroup
Descriptions
Retrieving a List of Article Numbers
Retrieving a Specific Header Field
Searching for Articles by Header
Server-to-Server Communication
Using the cfNNTP Object
Epilogue
CHAPTER 5—ELECTRONIC MAIL
Introduction
The SMTP Protocol
SMTP Commands
Server Responses
Reply Code Categories
VB Programming Technique
Brain-Dead SMTP
True SMTP
Connecting and Disconnecting
Sample Application: SMTP.VBP
Sending Mail
Sending versus Mailing
Replying to Mail
Forwarding Mail
Verifying an SMTP Address
Error Handling
Post Office Protocol 3 (POP3)
POP3 Commands
Server Responses
POP3 States
Authorization State
Transaction State
Update State
VB Programming Technique
Sample Program: POP3.VBP
Logging into the Server
Retrieving Message Headers
Retrieving Messages
Sending and Receiving Binary Files
How UU Encoding Works
UUCODE.BAS Encoding and Decoding Routines
UUEncode
UUDecode
Sending an Encoded File with SMTP
nSendFileAsMsg
Using the cfSMTP and cfPOP3 Objects
Epilogue
CHAPTER 6—FILE TRANSFER PROTOCOL
Introduction
When Should You Use FTP?
The FTP Program
Connecting and Logging In
Listing Directories
Changing Directories
Downloading
Uploading
Supported Commands
Ending the Session
Using a Web Browser to Download Files
The FTP Protocol
FTP Errata
Connections
FTP Commands
Server Responses
Reply Code Categories
Visual Basic Code
Using a Display Terminal
FTPLogon
SendFTPCommand
Retrieving a Directory Listing
Changing Directories
Downloading a File
GetFileFromURL
Uploading a File
Debugging
Inside the FTP Code
Connecting to the Server
Reality Break
Inside SendFTPCommand
Changing Directories
Creating a Data Connection
Retrieving a Directory Listing
Unix Wildcards
Uploading a File
Downloading a File
Using the cfFTP Object
Epilogue
CHAPTER 7—ACCESSING THE WORLD
WIDE WEB
The World Wide Web
HTTP—Hypertext Transfer Protocol
HTML—Hypertext Markup Language
Understanding the World Wide Web
How to Read a URL
HTTP Message Headers
Interpreting the Server’s Response
Accessing HTTP Servers in Visual Basic
Accessing Forms
A Brief Overview of the Common Gateway
Interface (CGI)
Mapping with the TIGER Map Service
Sample Application—MAP
NetPaper
Tips for HTTP Programming
Further Reading
Epilogue
CHAPTER 8—AN INTRODUCTION TO
OBJECTS IN VISUAL BASIC
Introduction
Remember Type Variables?
More Analogies
How Do We “Make” an Object?
Properties
Collections
Epilogue
CHAPTER 9—USING THE CFINTERNET
OBJECTS
First Things First—cfWinsock
Using the cfWinsock Object
The Control Property
Inside cfInternet
cfNNTP
Retrieving Articles
Posting an Article
cfSMTP—Simple Mail Transport Protocol
cfPOP3—Post Office Protocol 3
cfFTP—File Transfer Protocol
Epilogue
CHAPTER 10—CGI4VB: SERVER-SIDE
PROGRAMMING
The Common Gateway Interface (CGI)
CGI4VB
CGI Speed Issues
HTML Forms and the ACME.HTM Sample Form
Form Definition
Field Definitions
The Submit Button
Hands-On CGI
CGI4VB.BAS
ACME.BAS: CGI_Main and Inter_Main
Dissecting Sub Main in CGI4VB.BAS
CGI_Main: Where the Magic Happens
Retrieving and Saving the Data
Sending Data to the Client with the Send
Command
The Status Code
Other CGI Options
Epilogue
CHAPTER 11—MICROSOFT INTERNET
INFORMATION SERVER
IDC–The Internet Database Connector
Understanding File Types
HTML Reserved Words
Active Server Pages
Accessing COM Objects in ASP
Hands On
ASP and Database Access
Processing Input Data from a Form
Returning Data to the User
IIS Applications in Visual Basic 6.0
Peer Web Services
WebClass Designer
HTML Template WebItems
Custom Tags
Custom Events
Custom WebItems
Testing and Debugging
Calling WebItems Manually from HTML
Epilogue
CHAPTER 12—Writing Custom Winsock
Client/Server Applications
The cfSocket ActiveX DLL
The cfSockClient Client/Server Model
Registering the cfSockClient Object on Your
Computer
Using a cfSockClient Object
Inside the cfSockClient OLE Server
Initialization
Connecting to the Server
Sending Data to the Server
Receiving Data from the Server
The Debug Flag
Sending a File to the Server
Receiving a File from the Server
The CFServer Application
Easy To Modify
Receiving Unsolicited Commands from the Server
Remote Data Access
ODBC_OPEN
ODBC_QUERY
ODBC_CLOSE
ODBCTest: A Sample ODBC Client Application
Epilogue
APPENDIX A
APPENDIX B
APPENDIX C
APPENDIX D
APPENDIX E
INDEX
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To access the contents, click the chapter and section titles.
Visual Basic 6.0 Internet Programming
(Publisher: John Wiley & Sons, Inc.)
Author(s): Carl Franklin
ISBN: 0471314986
Publication Date: 02/01/99

Brief Full
Advanced
Search this book:
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FOREWORD
Well, here we are again. Another version of Visual Basic (VB), a new
operating system, a new family of microprocessors, and another Internet
programming book and fortunately for me, there aren’t that many other VB
Internet programming books on the shelves, and I’m not complaining a bit.
The topic of Internet programming in Visual Basic spans many tools and
technologies. Many of these tools operate at a higher level than the code in this
book, while some operate at a lower level. I chose to write the example code at
a low enough level so that you can understand the processes, but high enough
so that you’re not completely focused on code that does the arduous tasks of
communications.
Winsock is a library of functions and routines that all Windows programs use
when they want to access the Internet. It provides the low-level functions of
sending and receiving data, as well as tools for managing connections, and
everything else that has to do with basic Internet communications.
My code uses a Winsock control for communications, whereas some other
books opt to access the Winsock library directly. I believe that it is neither
beneficial nor necessary to do this. The real bottleneck in Internet
communications is the Internet connection itself. You don’t gain anything by
saving a few nanoseconds, if indeed you actually can. If you really want to get
the best performance, get a faster Internet connection. The benefits you gain by
programming at a higher level are too numerous to ignore.
That said, there are other books that focus on higher level tools that do
everything for you. You just tell a control to send an email message and it just
happens. While most of the time this approach works great, there may be
situations in which you need to make changes in the process due to the quirks