APPENDIX B. USING A MODEM
Using a modem (modulator-demodulator) is relatively easy if you follow the instructions that come with the modem and the communications software. These instructions cannot
BUYING A MODEM: BASIC FEATURES
You should choose a "Hayes-compatible" modem. This is the industry standard and works with most software. The modem is a small computer that responds to "AT" commands, commands sent by your software beginning with "AT" for "Attention Modem". The most common are "ATDT 1 800 555 1212". This tells your modem
So make sure the modem you buy responds to AT commands. A 2400 baud Hayes-compatible modem will cost about $50 by mail-order. You should consider buying a FAX modem ($350), however. The more expensive modem is faster, has more features, and can turn your computer into a FAX machine. Your connection to the outside world will never be any better than your modem allows, so buy a good one.
The FAXes can be displayed on your computer screen. You only print them if you want to, on an ordinary laser printer. The other features of a top of the line FAX modem include:
(1) Up to 14,440 baud rate (7 times faster than 2400 baud)
(2) Data compression (V.32bis is the name of the standard)
(3) Error correction (V.42bis is the name of the standard)
HOOKING UP THE MODEM
The modem goes between your computers serial (one-bit-at-a-time) communications port and your telephone line. Your modem probably included the right kind of cable. If not, check the manual or call the dealer who sold you the modem.
The modem to phone connection will use standard telephone cable with modular jacks on either end. You unplug your phone from the wall socket and plug in your modem instead. If you want to leave your phone, answering machine, fax machine, and so on plugged in, you can use dual plugs that allow one or more cord to be plugged into the same socket. Look on the bottom of each piece of equipment (including the modem). There should be a little sticker that tells how many ringer equivalents the equipment is worth. Don't exceed eight on any one phone line.
You can also buy inexpensive boxes that will let you use a single phone line for faxes and for voice.
WARNING: usually your modem—and any other "peripherals"—should be wired to your computer before you turn the computer on. This is so the computer can look for the modem and confirm that it is hooked up. Check your computer's and modem's manual for precise instructions on hooking up a modem to your computer.
If you are connecting the computer to an office phone that is part of a
Private Branch Exchange (PBX) then …
MAKING A CONNECTION
Usually you call another computer by dialing its phone number. Either you type an AT command like "ATDT 1 800 555 1212" or your software does this for you when you choose a "connect" command or something like that from a menu.
Before you get the modem's attention you need to set your software to the proper "modem settings". These settings are listed in literature about the service. As a last resort call customer service for the computer you are trying to connect to. Or else you can try different settings until you find one the lets you connect. The most common modem settings today are either 1200 or 2400 baud and "8N1", which means 8 bits, no parity, and one stop bit.
The most important settings are:
The BAUD RATE (300, 1200, and 2400 are typical low speed connections, with 2400 being the most common one for modern equipment; 9600 or 14400 are
Flow control ON or OFF (often labelled XON/XOFF). If your modem is going to talk with your computer at a faster rate than over the phone line, then flow control is essential. Be sure that your software understands that the phone line speed is different from the computer-to- modem speed. The phone line can't go any faster than 14,440 Baud. Your computer can do four times that or more.
Full or half duplex connection (LOCAL ECHO ON or OFF). In a half duplex connection the two computers take turns communicating on the same channel. This means that your computer will be the one to "ECHO" what *you* type on your screen (local echo ON), since it doesn't make sense say something, have the other computer read it, then send it back, just so you can see what you type. In a full duplex connection both computers can talk at once, so local echo is OFF.
7 or 8 bits per character. Many computer systems use the last seven bits of each byte to denote a character (up to 128 characters). The eighth bit is used for parity, flow control, or some other important signal. Nowadays 8 bits is more common.
Even, Odd, or No PARITY. One way to check for errors in transmission is to tag each byte with a bit that means "even or odd", the parity bit. If a bit is transmitted incorrectly, then the parity bit won't agree with byte sent and the software can ask for that byte or block of data again. NO parity is the most common setting today, however.
0,1, or 2 STOP BITS. 1 stop bit is the usual setting these days.
If your modem has its speaker on, you will here a dial tone, then the modem will dial, and then there will be a lot of squeals as the two computers "negotiate" about the transmission. If you are lucky, both computers will establish a "carrier" tone or hum that is then modulated to send data. At this point most modems turn of the speaker, but a "carrier detect" light should be on. As long as you have the carrier you have the connection. The carrier is present—to your modem, at least—even if you tell your software to "go off line" for a while. If you hang up, however, the carrier is dropped.
Now that you have a carrier, whatever you type is sent to the other computer (and the "transmit" light flashes), and you can receive data as well. Pay attention to any banner the service you are connecting to may print. In particular you need to know what "escape character" your system recognizes. Typing this character or sequence of characters allows you to stop tranmitting everything and give your own system a command. This is especially important if are transferring a file and have to "escape back to your own system" to tell it what to do with the incoming data.
FIRST STEPS ON A NEW SYSTEM
Many services let you sign up by connecting your computer to a
TRANSFERRING DATA
Getting data from one computer to another is a matter of running *two* programs—one on each computer. These programs use a common protocol, or procedure, to communicate. The most common protocols are XMODEM, YMODEM, ZMODEM, and KERMIT (for UNIX systems and some others). The steps involved—using KERMIT as an example—are:
1. Run KERMIT on the sending machine
2. Escape to the receiving machine
3. Run KERMIT on the recieving machine
4. Wait for the transfer to finish.
You will have to read your software manual for more specific instructions, unless you have a direct internet connection or SLIP connection. In these cases you can issue a File Transfer Protocol (FTP) command to whichever computer and the details at the other end are automatically taken care of. See Chapter X for more detail on transferring data.
DISCONNECTING
You will want to use whatever "logoff" procedure the remote computer wants. If your manual or other literature doesn't tell you, and you can't get any information by trying "help" or "?", try the following commands: "logout", "logoff", "lo", "bye", "exit", "quit".
If all else fails you can drop the carrier using the "hangup" command (or escape back to your system and send "ATH" to your modem—attention, hangup).
As a last resort pull the plug and your telephone company will disconnect you, then exit your software and turn off your computer.
You may have to get your modem's attention by typing the "escape
sequence", which varies from modem to modem or connection to connection.
<Appendix C> Technical Details of Internet Connections
[This chapter is under construction]
<Appendix D> Just enough UNIX
Since the UNIX operating system may be unfamiliar to many of you, and since many workstations on the net use UNIX, it may help some readers to summarize some of the peculiarities of UNIX. One day you may be logged on to a UNIX machine. Nowadays, like many operating systems, UNIX hides behind a graphical user interface like the X Windows system. Occasionally—and networking is unfortunately one of those occasions— its quirks like file-naming and directory hierarchy peek through.
This Appendix gives you just enough UNIX to avoid some pitfalls and issue commands needed to transfer files. The basic commands you need to know for any system are how to display directories and list the contents of files, how to name files, and how to get help about the system. UNIX commands are just as quirky as MS-DOS, VMS, RSX, VM, or any other operating system that uses a command language. Fortunately, they are no harder.
<Section D.1> Basic Commands for Getting Around
ls : list current directory
ls -l : longer listing, with file length in bytes
cd mydir : move down one level in the hierarchy to directory "mydir"
cd .. : move up one directory in the hierarchy
<Section D.2> Hierarchical File System
Files in UNIX are arranged in a hierarchy or tree structure.
<Appendix E> The Top 10 Things to Get by E-mail
This Appendix may be distributed separately from the rest of this course.
—————(cut here)————— THE FREELORE PROJECT's LIST OF THE TOP 10 THINGS TO GET BY E-MAIL
Copyright (c) 1993 by John E. Goodwin. All Rights Reserved. You may make and distribute verbatim copies of this document for non- commercial purposes provided this notice is preserved on all such copies.
This is a list of ten fun and useful things you can get by electronic mail. In all cases your request is handled by an automated system that sends the materials by return mail. Systems change frequently, so some commands may be out of date. All were tested and working as of mid-June 1993.
A typical, old-fashioned E-mail system works like this
% mail <type the command to enter the E-mail program>
mail> send <or type "help" to find out what commands work>
To: president@whitehouse.gov <This is an Internet address
—may look different on your
system>
Cc: vice.president@whitehouse.gov
Subj: Your Stance on Nuclear Power
Enter Message. When Done, hit Control-Z, Control-C to quit:
Dear Mr. President:
I was disappointed to see that . . . <etc., until you type CTRL-Z>
Message sent 23:05:44 14-JUN-1993.
mail> exit
Modern automated mailservers expect your command in the body of the message. But some old-fashioned ones expect it as part of the *subject* line! I always tell if this is the case.
In most cases you will get a response in a few minutes. For systems that wait to off-peak hours to send responses you may have to wait a day.
Here are some more hints:
o Most automated systems respond to the single command "help".
o People change their directory systems around everyday it seems. If the commands given don't work, try to locate what you want by Archie (see below) before requesting it by mail.
o The Double quotes around some commands aren't part of the command itself (so don't type them!).
With that advice, here's the list. . . .
[10] The CPET (Catalog of Projects in Electronic Text) supplies information about E-text archives for scholars. They have an online database. For detailed instructions, send the message:
connect guvax.acc.georgetown.edu cd cpet_projects_in_electronic_text get cpet_user_guide.txt
to "ftpmail@decwrl.dec.com". [This is a service that provides Internet File Transfer Protocol (FTP) by E-mail. See next entry].
Anonymous FTP reference for CPET user's guide:
"guvax.acc.georgetown.edu:/cpet_projects_in_electronic_text/cpet_user_gu ide.txt"
[9] Instructions for using Archie by Mail and FTP by Mail.
Archie is a lookup service for finding software or documents in Anonymous FTP archives on the Internet. Anonymous FTP is a method for making materials on certain computers available to the public. Anyone is allowed to log in with the username "anonymous" You give your real name as the password. Anonymous FTP is not available if you just have E-mail, not a full Internet connection.
To help E-mail users access Anonymous FTP archives, an FTP by Mail server has been set up at decwrl.dec.com. It will send you materials you find using Archie. Binary files (pictures and programs) are encoded as text files using the programs "btoa" or "uuencode". You need these freeware programs if you want to get anything besides text files, i.e. ASCII.
A. To get started with Archie, send the message "help" to "archie@archie.rutgers.edu". There are many Archie servers around the world. Any Archie will give you a complete list.
B. To get started with FTP Mail, send the message
help quit
to "ftpmail@decwrl.dec.com".
[8] A list of book-length Public Domain texts Produced by Project Gutenberg.
You may either get these texts from the Almanac server at "oes.orst.edu" or direct from Project Gutenberg at "mrcnext.cso.uiuc.edu".
Send message "help" to "almanac@oes.orst.edu". After reading the guide, send the message "send gutenberg catalog". To get an E-text by mail (e.g. Alice in Wonderland), send the message:
send etext alice
To see the contents of project gutenberg archivesj, send the message
connect mrcnext.cso.uiuc.edu cd etext/articles get index quit
to "ftpmail@decwrl.dec.com".
To get the actual texts,
connect mrcnext.cso.uiuc.edu
cd etext/etext93
get
quit
Anonymous FTP Archive references:
oes.orst.edu:/pub/data/etext
mrcnext.cso.uiuc.edu:/etext/articles (general info)
mrcnext.cso.uiuc.edu:/etext/etext93 (the texts)
[7] A list of E-mail mailing lists, posted to the "Frequently Asked Questions" or FAQ part of the Usenet newsgroups.
A typical mailing list works like this: to join, say, a mailing list on politics, you send the request "subscribe" to "politics- request@whitehouse.gov". Thereafter, any message sent to "politics@whitehouse.gov" will send you message to all members of the list. You get all the postings from other members as well [The Whitehouse list on politics is a fake example].
Aside: Usenet newsgroup FAQ's are archived at "rtfm.mit.edu". They cover every conceivable subject (but are especially good with computers). To access the archive by E-mail, send the message "help" to "mail-server@rtfm.mit.edu". For an index of materials available, send the message "index".
Here are the specific commands for getting the Mailing Lists:
send mail/mailing-lists/part1 send mail/mailing-lists/part2 send mail/mailing-lists/part3 send mail/mailing-lists/part4 send mail/mailing-lists/part5
to "mail-server@rtfm.mit.edu".
Other good publications in the same location:
A Guide to Social Newsgroups and Mailing_Lists:
send social-newsgroups/part1
List of Periodic Informational Postings:
send periodic-postings/part1
(six parts).
For a more complete list of FAQs, send the commands:
send usenet/news.answers/index send usenet/news.announce.newusers/index
Anonymous FTP archive reference:
rtfm.mit.edu:/pub/usenet-by-group/news.answers; and rtfm.mit.edu:/pub/usenet-by-group/news.announce.newusers.
Also posted as an FAQs to the Usenet newsgroup news.answers.
[6] LISTSERVERS are the best thing going for persons with E-mail but without full Internet service. You can send mail to an entire list and get a digest of "articles" posted on a given day. Lists are espcecially good for anyone with an interest in the Humanities. A list of all listservers known to any one listserver can be obtained by sending a message to that listserver (see below).
Send the message "help" to any listserver address, e.g.
"listserv@brownvm.brown.edu"
to get started.
The listserver at Brown does not respond to the global command (but is worthwhile anyway). Try sending the command "lists global" to one of the other listservers like "listserv@auvm.american.edu".
For lists with lots of traffic you should consider the "set <listname> digest" command to get *one* mail message a day with a compendium of articles.
[5] Automatically supplied information about PSI's Internet service:
Send any message at all to address "all-info@psi.com". There are lots of other files on their service available instantly. E.g., for information on their version of telnet, send any message to "gds- info@psi.com"; for their version of FTP, any message to "psilink- info@psi.com".
[4] Scott Yanoff's list of Internet Resources. At last count, there were 75 free things to do on the Internet.
Send the message:
send usenet/news.answers/internet-services/faq send usenet/news.answers/internet-services/list
to "mail-server@rtfm.mit.edu".
Another method is to request the materials by delayed FTP with the message:
connect csd4.csd.uwm.edu cd pub get inet.services.txt quit
to "ftpmail@decwrl.dec.com".
It is also worth adding the line "get internetwork-mail-guide" to the above request for a file on send E-mail between any two E-mail systems (file is 22k).
Anonymous FTP archive references:
csd4.csd.uwm.edu:/pub/inet.services.txt
rtfm.mit.edu:/pub/usenet-by-group/news.anwsers/internet-services
[3] SURFING THE INTERNET, by librarian Jean Armour Polly. This must- have publication is still the best basic orientation to the Internet. The nearest thing to the "how to use the library card catalogue" speech that opened up that other world for us when we were kids.
Send the message
connect nysernet.org cd pub/resources/guides get surfing.2.0.3.txt <that's a zero not an "oh"> quit
to "ftpmail@decwrl.dec.com". Other interesting files in the same directory are:
ftp.list whatis.internet new.user.guide.v2.2.txt speakers_on_internet.txt
Anonymous FTP archive reference:
nysernet.org:/pub/resources/guides
[2] The NIXPUB listing of public access UNIX systems (so you can read Usenet news!):
Send the message
connect vfl.paramax.com cd pub/nixpub get long quit
to "ftpmail@decwrl.dec.com".
Anonymous FTP archive reference:
vfl.paramax.com:pub/nixpub/long
It is also posted as a FAQ (Frequently Asked Questions) to the Usenet newsgroup alt.bbs.
And the critics' choice is . . .
[1] The PDIAL listing, a listing of dialup methods of connecting to the Internet for the general public.
Send a message to "info-deli-server@netcom.com" with the command
"send pdial" in the *subject* line.
Alternatively, send the message "send usenet/news.answers/pdial" to "mail-server@rtfm.mit.edu". —————
+ + +
"What this country needs is a good 50 cent education."