[Western Oregon University]



File Transfer Protocol

The method by which files are transferred between computers on the Internet is called File Transfer Protocol (FTP). There is a wealth of computer programs, data files, sound files, graphic files, etc. available on the Internet. These resources are available to download (copy) using FTP.

The Internet was developed to allow resources to be shared between computers. Since the Internet is a distributed system, a program useful to a number of people need not be stored on each individual's computer. Rather, the program can be located on a single computer and accessed by several users at the same time. Thus, the ability to access computer programs on remote computers decreases the amount of hard drive storage an individual needs on his/her local machine. You can transfer files between two computers on the Internet if you maintain an account on both computers or if you use the anonymous account on the computer containing the archive of files. The following is a list of some materials that can be transferred via FTP:
To transfer files, you must have an FTP client program running on the local computer. This client program converts the commands issued by your computer into a universal set of commands that will be understood by the remote FTP server and asks the server to either accept a program from your local computer (upload) or send a file to your local computer (download). After receiving the commands, the server processes the request and returns or accepts the items requested. Although the client program is written for a certain computer platform, it can transfer files between computers of different platforms. Thus, files can be transferred between a DOS machine and a Macintosh or UNIX machine.

In reality, when you download a file from a remote server, the actual file is not transferred. Rather, the FTP server reads the contents of the file and sends a copy of it to your local computer which stores it. The Internet software ensures that nothing destroys the contents of the file.

FTP is not the only way to transfer files on the Internet. Many Web browsers can link to an FTP server for downloading files. Web browsers do not allow uploading. Data and text files can be attached to email messages and sent to a remote computer. Beware, if the e-mail software on the two computers is not completely compatible, the transferred file may be rendered useless. FTP is a fast, easy and efficient way to transfer files between computers.

Using FTP

Logging On To An FTP Server

Once you have installed FTP client software on your local machine, you are ready to contact a remote computer. First, you must obtain the address of the machine with which you want to communicate. Once you know the address, you can connect with the remote computer and log onto the anonymous FTP server. All public archives allow you to use anonymous FTP. Type anonymous for user name and your e-mail address as your password. Since most FTP sites limit the number of anonymous logins, you may have difficulty connecting. TIP: anonymous FTP is most easily done during off-peak hours.

Navigating Within An FTP Site

The files stored at an FTP site will be stored in directories and subdirectories similar to those found on a computer's hard drive. You can use your FTP connection to navigate through the directory structure to find what files reside in any given location. Typing the commands "dir" or "ls" will generate a listing of files or directories available. Sometimes a subdirectory will contain an index file which identifies the files residing there. It is also important to determine the file format for your desired file and whether the file is compressed or uncompressed. Accurate transfer is dependent on providing this information to the FTP. The two most common file types are:
A file transfer type of binary will usually work for both ASCII and binary formats so if you are not sure what the format is for the file to be transferred, use binary. If a compressed file is to be transferred, you must have a decompression program compatible with the compression format to be able to use the program.

Common FTP Commands
commandexampleexplanation
ASCII or textftp>asciiset file type to ASCII
binaryftp>binaryset file type to binary
bye, close or exitftp>closeend FTP session
cd directory-nameftp> cd chemistrychange working directory on remote computer
dir, lsftp>dirlist directory on remote system
get file-nameftp>get funstuff.dattransfer file from remote server
help or ?ftp> helpshow FTP online help
lcdftp>lcd mydirchange working directory on local computer
mgetftp>funstuf1.dat funstuf2.dattransfer multiple files from remote computer
mputftp>funstuf1.dat funstuf2.dattransfer multiple files to remote computer
openftp>open ftp.remote.comopen connection to apecified remote computer
putftp>put funstuff.dattransfer file to remote computer
pwdftp>pwddisplay working directory on remote computer
userftp>anonymousspecify user name to remote computer

Searching For Files

How can you locate a file of interest among the myriad of files spread across the Internet? You can use a tool called Archie, a general search engine, a jumplist, or a software specific search site.

Archie

Archie is a server which collects lists of files and their associated directory information from anonymous FTP sites and stores the lists in an indexed database which can be searched via keywords. The Archie server will return a list of file names and FTP site locations that match the keyword. Archie does not canvas all FTP sites, but rather, those FTP sites whose administrators allow searching.. Although Archie updates its database regularly, your search of the Archie database may return files that are no longer available or miss files that have been recently added to an FTP site.

Ways to Access Archie Servers:

Archie servers tend to be busy so it is best to use them at off-peak hours. Archie servers normally process interactive logins first and processes email requests when demand on the server is low. Although email takes longer than other methods, it has the advantage of providing a printout of search results which can be saved as a file for later use.

Some Archie Servers
ds.internic.netUSA
archie.sura.netUSA
archie.unl.eduUSA
archie.rutgers.eduUSA
archie.auAustralia
archie.uquam.caCanada
archie.doc.ic.ac.ukUnited Kingdom
archie.funet.fiFinland
archie.th-darmstadt.deGermany
archie.ac.ilIsrael
archie.unipi.itItaly
archie.wide.ad.jpJapan
archie.nzNew Zealand
archie.luth.seSweden


Archie Via Email

Using Archie via email involves writing a message that contains the necessary search commands and sending it to one of the Archie servers. The following example shows how you could search for a copy of the file decompression program pkunzip.exe.

From: courtna@wou.edu
To: ds.inernic.net
Subject:

find pkunzip.exe

The Archie server will search its database and send you an email message listing sites and identify the subdirectory in which the file resides.
Guidelines for Messages:
If you use an invalid command in the body of your message, the Archie server will disregard the line containing the invalid command.

Search Engines, Jumplists, Software Specific Sites

If you know the complete or partial name of a file, you can search for it using a search engine such as Infoseek. YAHOO! is useful for locating sites containing Jumplists or lists of links to sites having specific categories of software.

Jumplists are useful because they often list the most recent versions of unique and useful software for a specific interest area. Often jumplist authors include reviews or descriptions of the software. An example of a jumplist of Internet related software is located at Tucows (http://www.tucows.com).

Software specific search sites can be used either to find a specific file or search through general software categories. Typically, the sites divide their lists by computer operating system (Windows, Macintost, UNIX) and the subdivided by category.

c|net's Shareware.com is a software specific search site where you can locate software by filename or search using keywords that occur in filenames or file descriptions. Shareware.com does not maintain copies of the files listed in its database, but rather, provides links to FTP sites from which the file can be downloaded.

When you access shareware.com, you will be presented with a screen that offers a Quick Search option as well as links that offer more advanced search options. When searching, you will be able to restrict your search to to a specific operating system or environment. Using this feature will allow you to narrow your search by weeding out files that you can't run on your system. You can limit your search to programs that run in Windows 3.1, Windows 95, Windows NT, all the Windows environments, Macintosh, DOS, OS/2, UNIX, Netware, Amiga, and Atari.

Shareware.com conducts its search in a somewhat different manner that other search engines. Shareware.com uses your search words as "raw" words rather than keywords. In a keyword search, the search engine looks for the keyword and only returns results that match the entire word. In a raw word search, the word is viewed as a sequence of letters. The search engine will return results are similar in sequence. Thus, entering per as your search word would return period and periodic as well as hyper and operator. If you want to widen your search, search with a short sequence of letters. If you want to narrow your search, use a longer sequence of letters.

Only one word can be used in Quick Search so this is most useful if you know the specific name or part of the name of the file for which you are looking. For most other searches, more advanced search options will be more efficient. Shareware.com provides an advanced Quick Search which allows a second word to be added to your search. The two search terms may be related using the AND and OR Boolean operators. AND returns results that contain both words which lowers the number of hits while OR will increase the number of hits. The most powerful search option is the Power Search which is accessed from under the Other Search Options graphic.

After you enter your search statement, Shareware.com will carry out the search and return a list of files which meet your search criteria.

Downloading The File

Once you have located a file of interest, you need to obtain a copy of the file. When you click on the desired file, Shareware.com will load a new page that lists links to servers from which you can download the file. Shareware.com requests that you try to download the file from the site that is geographically closest to you because this results in an efficent use of internet resources. If you are unable to get the file and can't wait, try to download from a distant site where the time is between midnight and 6 AM. Popular FTP sites are usually very busy, and you may have difficulty establishing a connection during peak hours. The best time to download files is about 3 AM EST and the worst time in between 1 PM and 3 PM EST.

Downloading the file is easy. Click on the site from which you wish to download. If you are using Netscape Navigator, the Save As dialog box will open. Type in the drive to which you wish to save the file. If the site that you have chosen is busy for a connection to be established, a notice will be displayed that explains that the site is too busy and suggest that you try at another time. At this point you can go back to the download page and choose another site or wait a short time and try again.

If the you don't have the appropriate helper application to actually use the file loaded into Netscape, the Unknown File Type dialog box will be displayed. This will not affect you ability to save the file.

Using An Internet Browser

If you know the address for an FTP site, you can go directly to that site in Netscape by typing in the URL for that site (ftp://ftp.somesite.com). Netscape Navigator will carryout the anonymous login for the FTP site for you. Usually, a set of tips and guidelines followed by a list of links to the server's directories will appear on your screen. Following the links should lead you through the structure of the server until you find the desired file. Often, there will be text readme or index files available to describe the contents of the various folders and files. Once you have found the desired file, click on the link and download in the manner described for Shareware.com.

To try this out, access Netscape's FTP site at ftp://ftp7.netscape.com/. When you enter a site, if no readme or index files are listed, look for a pub directory. This directory often contains files likely to be of general interest.

Netscape's automatic login process works well for anonymous FTP sites, but not always for private FTP sites. These site will issue you a specific username and a password that you must use to gain access to the site. Sometimes these sites will request this information upon accessing their page. Other sites will require you to add your username and password to the URL in the format ftp://username:password@ftp.somesite.com/. Some sites meld the two methods together so that the username is added to the URL and the password entered into a dialog box after the page is accessed.

ABOUT FILES

File Types

There are a number of different file types that you may encounter in your FTP voyages. The following list shows some of these file types and their file extensions.