Preface

The 4D Internet Commands empower users of 4D with a robust set of communication utilities capable of working in either a Local or Wide area network. The ultimate expression of this explosion of connectivity is known colloquially as "The Internet". The last few years has produced phenomenal growth in the number of people and companies gaining access to the Internet. As the volume of people with Internet access increases, the need to be "on the net" is felt more and more each day by those in the business community.

The suite of commands provided by 4D Internet Commands gives database developers access to many key elements of the Internet. The SMTP commands contain tools to automate e-mail delivery from a database to any list of people. Similarly, the POP3 and IMAP commands can retrieve mail from any number of mailboxes for storage within the database, re-routing, auto-reply or remote-search execution. The FTP commands enable the user to transfer files to/from remote systems or to obtain directory listings of files on FTP volumes. And both the TCP and UDP commands provide developers with the low-level tools enabling them to accomplish any internet-related task.

SMTP (Simple Mail Transfer Protocol) is the primary mail transfer protocol used over the Internet. 4D Internet Commands allow users to quickly build and send mail via a SMTP server. Mail creation and delivery can be as simple as a single command. If your mail delivery needs are more complex, every aspect of the message header, body and attachments can be controlled to affect its delivery. Since Internet mail addressing provides for delivery to such services as CompuServe, America Online, eWorld, etc. you are able to reach virtually anyone with an e-mail account. Other examples of how the suite of SMTP commands could be used are:

• Automation of database report delivery
• Creation of an automatic mail forwarding database
• Group mail-list management
• Store-and-forward remote database updates & synchronizations

Along with its SMTP commands, 4D Internet Commands also contains commands that will connect either to POP3 (Post Office Protocol, Version 3) or IMAP (Internet Message Access Protocol) mail servers for retrieval of mail messages and encoded attachments. Since the suite of SMTP, POP3 and IMAP commands conforms to the MIME standard for multiple message enclosures, binary attachments can easily be downloaded and saved.

The commands also provide users with the ability to encode attachments in several different ways such as: Binhex, Base64, AppleSingle, AppleDouble...

The FTP (File Transfer Protocol) commands provide a very easy-to-use mechanism for communicating with an FTP server to send/receive text or binary files. Commands within the FTP suite can obtain directory listings of files, enabling the database developer to create navigable interfaces to remote volumes of files. The FTP commands can easily be used in document-tracking applications without requiring client applications to mount remote volumes directly.

Transmission Control Protocol/Internet Protocol, (TCP/IP) is the primary protocol used for sending and receiving data over the Internet. 4D Internet Commands contains several commands for sending and receiving raw TCP packets. The TCP set of commands provides developers with the essential tools to build and control their own Internet communications. In addition, the TCP_Open command allows connection using a SSL (Secured Socket Layer) protocol.

Some examples are:

• Build your own telnet interface
• Execute shell commands on remote machines
• Retrieve documents from the World Wide Web
• Search through numerous on-line databases
• Handle database synchronizations with remote servers
• Federal Express and UPS package tracking
• Connect to a Web server in Https.

Note: For greater flexibility, 4D Internet commands let you pass a POP3, IMAP or FTP connection reference directly to low-level TCP commands and vice versa. For more information, refer to the Low Level Routines, Overview section.

The UDP protocol is an easy-to-implement protocol for sending data that is faster and simpler than TCP, but with lower reliability since it does not allow delivery verification, error-checking or recovery of data that was improperly delivered.