Why is it so hard to say good-bye? Sometimes the biggest problem new users have using publicly available services is getting out of them without shutting down the computer or turning off the modem. When you're remotely logged in to another computer, everything you type is being sent to the remote system for execution. There are two ways to exit a system. One way is simply to logout of the service. Unfortunately, there's no standard "let me go" command. The best advice is to read with care any instructions that show up when you login to a system. If the screen doesn't tell you anything, try one of these commands: exit, quit, logout, leave, bye, goodbye, ciao, disconnect, CTRL-D, CTRL-Z.
If you still can't exit, then you can terminate the session by signaling your local telnet program that you wish to quit. Using a special "escape" character or command allows you to suspend your telnet session temporarily, and you're brought back to a telnet prompt (usually telnet}) on your home system. The escape character can vary, but on many systems it's a CTRL-]. (Hold down the control key and at the same time press the "]" key.) On some systems, CTRL-^ is used. You can then quit the telnet session by typing quit at the telnet prompt.
The Weather Service is neat, but it's just the tip of the tornado! There's much, much more. Here's an idea of the types of resources that are accessible via remote login and how to try some of them out.
Some of the most common and most often mentioned Internet resources are the online library catalogs. At least 500 catalogs are accessible via the Internet, mostly at academic organizations all over the world. Most don't allow you to look at or transfer entire online books; they just let you review bibliographic records. You can peruse a certain library's collection, verify a citation or reference, or see if a book is checked out or if it's available through the interlibrary loan system. Online library catalogs, by the way, are usually open all day and all night!
Some online catalogs offer more than just bibliographic records. For example, to explore the UHCARL Library System at the University of Hawaii, Manoa, type:
At the enter class prompt, type lib. Select 5 for VT100 emulation. Wander through the menus. (See if this book is in the database!) Items of interest include an index of Hawaiian sheet music and the 1993 edition of the Hawaii Data Book. Some online library catalogs even offer access to online encyclopedias. Not every service offered in the menus may be available to outside users. For example, most online encyclopedias may be limited to registered users because of licensing restrictions.
plokta /plok'ta/ (Acronym for 'Press Lots of Keys To Abort") v. To press random keys in an attempt to get some respoinse from the system. One might plokta when the abort procedure for a program is not known, or when trying to figure out if the system is just sluggish or really hung. Plokta can also be used while trying tofigure out any unknown key sequence for a particular operation. Someone going into plokta mode usually places both hands flat on the keyboard and presses down, hoping for some useful response.
In addition to online library catalogs and commercial services, there are many other types of services you can access via remote login.
Bulletin Board Systems. Bulletin board systems (BBSs) on the Internet are a lot like the electronic bulletin boards that you can dial into using a modem. Most BBSs offer a menu of services. Some supply conferencing capabilities, while others provide "read-only" information, similar to regular bulletin boards at a library, where information is tacked up for everyone to read and taken down when it's no longer relevant.
FreeNets. FreeNets are community-based bulletin board systems with email, information services, interactive communications, and conferencing. Funded and operated by individuals and volunteers--in one sense, like public television--they're part of the National Public Telecommunication Network (NPTN), an organization based in Cleveland, Ohio, that is devoted to making computer telecommunication and networking services as freely available as public libraries. The FreeNet concept-- promoting community networking--is catching on, and they're opening up in more and more cities. Access is usually by a local phone call using a modem, and a good number have connections to the Internet.
A popular FreeNet is the Tallahassee FreeNet, which is organized like a small city. Thousands of people access this system each day, chatting with each other and visiting the Government Complex, the Library, the Science and Technology Center, or the Home and Garden Center. Want to try it? Here's the command to visit the Tallahassee FreeNet:
If you're a first-time user and don't have an account, you can demo the system by selecting the visitor login choice. From there you can apply for an account free of charge, if you wish, or you can just explore the system.
SpaceMet Internet telnet spacemet.phast.umass.edu NASA Spacelink telnet spacelink.msfc.nasa.gov
(New users login with the newuser id and newuser password.) Center for Advanced telnet cass.jsc.nasa.gov Space StudiesLogin as cass; password: online NASA/IPAC Extragalactic telnet ned.ipac.caltech.edu Database (NED)Login as ned
Imagine that you're creating an important report at your personal workstation. You want to print it out, but you don't have a printer nearby. So you copy the document onto a floppy, put on your Keds, and run down the hall to load the floppy at the nearest workstation-printer site. This process is known as file transfer, because the report is being transferred to another computer. If both computers were on the Internet, you could have transferred this file in a matter of seconds using the file transfer capability. Instead of sending the file through the slower "SneakerNet," you could have sent it over the electronic highway. In short, the file transfer capability gives you the ability to copy files from one computer to another.
A file can be anything. It can be a document you create in your PC's word processor. It can be a spreadsheet or a software program. It can be a picture, or even music. Or it can be ASCII (American Standard Code for Information Interchange) text, which is plain text with no formatting codes, such as boldface or underlining.
Many of the documents are just text, readable no matter what computer or software you're using. You should be aware, however, that some of the files you transfer won't mean anything to the computer system you're using. A word processor document--one that was prepared by Microsoft Word, for example--has special typesetting codes within the document. Obviously, this file won't be useful if you don't own the Microsoft Word application. Similarly, a file can be a software application. Not all software will "run" or work on every computer. In fact, it's safe to say that there isn't one piece of software that will work on every type of computer.
Many people get file transfer and remote login confused because both applications allow you to connect to other computers and obtain information. File transfer is a more specific and straightforward tool. Its main mission is to transfer files between computers. You're not actually interactively querying another computer's database or using a service to find out any information.
There are also similarities and differences between file transfer and electronic mail. Email is used for transferring personal messages, although you can send and receive information in the form of files, too. You wouldn't use file transfer to deliver personal messages, but if you and another person need to transfer a file, such as a text document, back and forth, electronic mail will work just fine. Indeed, in most cases it is probably preferable, because you don't want to give another person your username and password. Two warnings, however. Some computers cannot handle extremely long email messages. If your file is very large, you may need to send it in smaller sections. Some email systems can also throw extra characters into your text, but file transfer guarantees integrity.
If the file is a non-text file, such as a software program, then it's almost always better to transfer it by using the Internet file transfer tool. As mentioned in Chapter 3, you can send non-text files, such as software and graphics, if your email application (and the receiving end) supports MIME, or if you have the necessary tools like BinHex to encode for transmission and decode upon reception. Since the latter process requires several extra steps, it may just be simpler to use file transfer rather than email.
Using the file transfer capability on the Internet is fairly straightforward. The protocol is called File Transfer Protocol (FTP). On many systems, the actual program that you will use is called ftp, which stands for "file transfer program." FTP allows you to connect to another computer and perform certain actions, such as listing the files in a directory and copying files back and forth between both systems.
To start a session, type ftp host-name. (Or you can also use the ftp command by itself, at which time you'll be put into the command interpreter, which waits for more instructions from you. The open host-name command will establish, or open, a transfer connection.) You should be prompted for your username and password on the remote system, just as in the telnet process. Once you've identified yourself to the remote system, you'll most likely see a prompt that looks like this: ftp>.
When you use FTP, be sure to check local system documentation for more information. It will tell you about the many other commands you can use and things you can do, as well as any system-specific characteristics you should know about. Keep in mind that most of the following commands will tell you information about and perform actions on the remote system. For example, you can find out what files are in the remote directory using the command dir (for "directory") or ls (for "list"). You can change to another directory where other files are stored using the command cd directory-name ("change directory"). To go back up the directory ladder to the parent directory, use the cdupcommand. If you don't know which directory you're in, the pwd ("print working directory") command will tell you.
If the changing directories part of this confuses you, then you need to understand that directories in computers are organized similarly to folders in a filing cabinet. A directory is basically an electronic folder with files and perhaps other folders in it, and when you change directories, you're just opening up a new folder. Once you're "in" the right directory on the remote system, you can do several things, two of which are getting a file (or files) and putting a file (or files). To download or transfer a file from the remote system to your local computer, use the get filename command. To upload or put a local file on the remote system, use the put filename command. You can always get help by typing help (for a list of commands), or help command. In fact, you should probably check out the help screens on any system when you are using it for the first time. When you finish transferring files, you can close the connection and exit by typing either bye or quit.
Many of the public archive sites run the Unix operating system, so if you're familiar with that, then the listing dir produces will make sense. If you're not, it may help to know that the Unix file system is a hierarchical directory structure similar to that of a DOS or Macintosh computer. (Hierarchical means that you start at the top, also known as the root, and work your way down through various directories.) Also, Unix is case-sensitive, so if a filename is shown in lowercase, then you must type it in lowercase. (A good rule is to always type the instructions or filename exactly as shown.) Chapter 6 ("Unix on the Internet: A Survival Guide") tells a bit about Unix commands and applications. Following is a sample listing of a directory on an anonymous FTP host that runs Unix:
-rw-r--r-- 1 tracy ftp 198 Apr 10 13:16 README
dr-xr-xr-x 2 root bin 512 Apr 1 1991 bin
dr-xr-xr-x 2 root bin 512 Apr 1 1991 etc
-rw-r--r-- 1 tracy ftp 88349 Aug 2 15:26 glossary
bin, etc, and pub are directories. The file creation date and time are easy to spot: README was created or modified on April 10 at 1:16 p.m. Another thing you should notice is the number immediately to the left of the date--the size of the file in bytes. The glossary file is 88,349 bytes, which is fairly large. Because it's so easy to transfer files, you may find that you can fill up your disk space quickly, so you'll need to implement a good file management system. Remember to delete the files you don't need and to compress the ones you want to keep. (A list of file formats and compression tools is included below.)
Copyright © 1994 by Tracy LaQuey and Editorial Inc.