The Online World Part 43

These weaknesses have given us better methods. Here are some of them:

XMODEM/CRC ---------- CRC is an abbreviation for Cyclical Redundancy Check. The method guarantees 99.9969 percent free transfer. It still has the other weaknesses of ordinary XMODEM transfers.

YMODEM Batch ------------ is faster than XMODEM and gives a high level of safety in the transfers. When used with some programs, YMODEM can transfer the files' creation time/date. You can transfer updated doc.u.ments. This will replace doc.u.ments with an older creation date. Only one party must enter the file name. YMODEM takes care of the rest.

Kermit ------ is used on many computer platforms, and especially where they use a terminal emulation mode (like VT-100) which makes the use of XMODEM impossible. Kermit is one of the few asynchronous error correction protocols that functions well when exchanging files having half duplex IBM front-end machines.

Kermit can transfer more than one file at the time.

Super-Kermit ------------ is also called Kermit with Sliding Windows. It can transfer many packets before stopping to check the transfer. The protocol is much faster than XMODEM.

ZMODEM ------ is currently the fastest transfer protocol for many applications.

All transactions are protected with a 16-bit or 32-bit CRC. ZMODEM is immune against most error conditions that prevent traditional protocols to achieve correct transfer.

ZMODEM transfers the creation date of the file and its exact contents. The file name is read once, and all transfer commands may be given by the sending program.

Decompression of files ---------------------- If a file has name extensions like ZIP, LZH, ARC, PAK, LQR, LBR, ZOO, ARJ, or QQQ, you are facing a compressed file. We use such files to achieve faster transfers.

Files having the extension .EXE or .COM may be compressed files that have been converted into a self-extract format. To retrieve the files from a self-extract compressed file, just enter the file's name.

To decompress files that have not been made self-extract, you need a utility program. These programs have many names and are available through most bulletin boards.

Transfer problems ----------------- Most transfer problems are caused by the communication programs and their (lack of) features.

Some Procomm users have problems with the Kermit protocol. Tip: use 8 bit world length and no parity in your program setup. 7 bits and even parity does not always work (on version 2.4.2).

Uploading --------- The transfer of data "the other way," i.e., from your disk to a remote computer, requires that you start by making some decisions.

Is the file to be sent as plain ASCII? Should I compress it in a distribution file to reduce transfer time, and make it easier to handle for the recipient?

If you are transferring a text file containing special national characters, then these may have to be converted to another format.

If your text contains blank lines (like blank lines between paragraphs), you may have to insert a s.p.a.ce character at the start of all such lines. Some systems interpret a blank line as a signal telling that transmission is done. The invisible s.p.a.ce character prevents this.

Some hosts have limitations on line length. They may require that lines be shorter than 80 characters. If you send lines that are too long, the result may be fatal.

Sending electronic mail ----------------------- If you send your mail too fast, some online services tend to get digestion problems. You must be very accurate with the format of your message. It has to agree with the host machine's rules about line length, and maximum number of lines per message.

Let's a.s.sume that you want to send the following message to an electronic mailbox:

To: Datatid cc: Anne-Tove Vestfossen Sj: Merry Christmas!

Text: Thanks for the box with herring. The taste was formidable. etc .. etc... etc...

Greetings, Odd

If this is all you have to say, doing it manually may be as fast as doing it automatically. However, if the line containing "etc .. etc .." is two full pages of text, you may feel differently. Then, the best may be to upload a prewritten letter.

Many Procomm users prefer to split the job in two. They enter the first four lines manually, and upload the body of the text (when the remote computer is ready to receive).

Press PgUp to get a menu of various uploading protocols. Select ASCII for transfer of plain text. Procomm will ask for the name of the file, which contains your letter. Enter the name, and the file will be sent.

Slow down with "pacing"

----------------------- Sometimes, the PgUp method is just what you need. On other days, strange things may stop you in the middle of your transfer. One typical reason is that Procomm is sending it too fast for the recipient.

"Pacing" is a method used to slow the speed of the transfer to a level that the recipient can handle.

Procomm lets you set a tiny pause after each line sent. Another technique is to ask the program to wait for a given character (a "Go-character"), before allowing it to send the next line. For example: the character ":" is often used in the prompts for the next line on bulletin boards.

Protocol transfers may be easier -------------------------------- You may find it easier to use a transfer protocol. With Procomm, press the PgUp key, and the program will ask for a protocol. Select Kermit or something else. The program will ask for a file name, you enter it, and off it goes. You will have no problems with blank lines, or lines that are too long.

At times, even this will fail. The most common reasons are: * The recipient requires that Procomm be set for 8-bits word length, no parity, 1 stop bit, when using this protocol, but you have it set differently.

* You think that the recipient's version of YMODEM is the same that you have. Wrong! Total failure.

Do the following to upload the file TEST.TXT to my bulletin board using XMODEM:

1. Navigate to the file area. Tell SHS what you want by using the following command: u;test.txt;x 2. Press PgUp, select XMODEM, enter a file name (TEST.TXT), and the transfer will start. (If you're too slow, SHS may be tired of waiting for your commands . . .) 3. When the transfer is completed, my board will ask for a short description of the file. Enter it, and you're done.

Enter G (for Goodbye), and disconnect.

Appendix 4:

Explanation of some frequently used terms =========================================

We have included some terms that are commonly used in the online world. For more information, get a copy of "FYI: Internet User's Glossary." To get this file, send email to [email protected] with the following command in the Subject of your mail: RFC 1392 .

Address ------- The string of characters that you must give an electronic mail program to direct a message to a particular person.

The term "Internet address" often refers to an a.s.signed number, which identifies a host on this network.

Anonymous FTP ------------- The procedure of connecting to a remote computer, as an anonymous or guest user, to transfer files back to your computer. See FTP for more information.

ANON-FTP -------- See Anonymous FTP.

ANSI ---- (1) ANSI is an organization that sets standards.

(2) 'ANSI graphics' (ref. the term ANSI-BBS) is a set of cursor control codes that originated on the VT100 terminal. Many online services use these codes to help improve the sending of characters to communication programs. It uses the escape character, followed by other characters, to move the cursor on the screen, change color, and more.

Archie ------ An electronic directory service for locating information throughout the Internet. You can use Archie to locate files on anonymous ftp archive sites, other online directories and resource listings. It is useful for finding free software.

Archie offers access to the "whatis" description database.

This database contains descriptions that include the name and a brief synopsis of the large number of public domain software, datasets and informational doc.u.ments located on the Internet.

This book emphasizes email access to Archie. You can also reach archie servers by telnet to one of the following addresses:

archie.au 139.130.4.6 (Australian server) archie.mcgill.ca 132.206.44.21 (Canada) archie.funet.fi 128.214.6.100 (Finland/Europe s.) archie.th-darmstadt 130.83.128.111 (Germany) archie.cs.huji.ac.il 132.65.6.15 (Israel server) archie.kuis.kyoto-u.ac.jp 130.54.20.1 (j.a.pan) archie.sogang.ac.kr 163.239.1.11 (Korea) archie.nz 130.195.9.4 (New Zealand) archie.ncu.edu.tw 140.115.19.24 (Taiwan) archie.doc.ic.ac.uk 146.169.11.3 (UK/England server) archie.rutgers.edu 128.6.18.15 (U.S.A.)

Archie server ------------- An email-based file transfer facility offered by some systems connected to the Internet.

ASCII ----- The American Standard Code for Information Interchange. A standard seven-bit code created to achieve compatibility between various types of data processing equipment. ASCII, p.r.o.nounced "ask-key,"

is the common code for microcomputer equipment.

The Standard ASCII Character Set consists of 128 decimal numbers ranging from zero through 127 a.s.signed to letters, numbers, punctuation marks, and the most common special characters.

The Extended ASCII Character Set also consists of 128 decimal numbers and ranges from 128 through 255 representing additional special, mathematical, graphic, and foreign characters.

ASCII download -------------- Retrieval of plain ASCII text (without special codes). Normally, it takes place without automatic error correction, but it is typically managed by XON/XOFF flow control.

Asynchronous transfer --------------------- Serial communication between two computers. When signals are sent to a computer at irregular intervals, they are described as asynchronous. Data is sent at irregular intervals by preceding each character with a start bit and following it with a stop bit.

Asynchronous transmission allows a character to be sent at random after the preceding character has been sent, without regard to any timing device. Consequently, in case of line noise, the modem can find out right away where the next byte should start.

Autodial -------- When a modem dials a telephone number automatically. Autodial may be started by the user entering the number manually, or the number may be sent automatically by the communications program (for example after having been selected from a phone register).

Baud ---- A unit of measurement that shows the number of discrete signal elements, such as bits, that can be sent per second.

Bits per second (bps) is the number of binary digits sent in one second. There is a difference between bps and baud rate, and the two are often confused. For example, a device such as a modem said to send at 2400 baud is not correct. It actually sends 2400 bits per second.

Both baud rate and bps refer to the rate at which the bits within a single frame are sent. The gaps between the frames can be of variable length. Accordingly, neither baud rate nor bps refer accurately to the rate at which information is actually being transferred.

BBS --- Bulletin Board or Bulletin Board System. See Bulletin Board.

Bell ---- Standard frequencies used in older modems made in the United States. The standard for 300 bps is called Bell 103. The standard for 1200 bps full duplex is called Bell 212A. Modems using these standards are normally unable to communicate with CCITT standard modems at these speeds.

Big5 ---- Coding scheme developed in Taiwan for using Chinese on computers.