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An FTP Primer I: The File Transfer Protocol Ray Beausoleil beausol@u.washington.edu Some of the most capable software packages currently available for microcomputers are publicly issued as either "freeware" or "shareware." Freeware is generously released by the author without charge, while shareware is distributed under a "try before you buy" agreement. Copies of many of these programs are archived on mini and mainframe computers throughout the world. If your local Unix site is connected to the INTERNET, then you may transfer these files to your site and download them to your microcomputer. FTP is the INTERNET standard File Transfer Protocol. The program "ftp" is the Unix user interface to the Internet protocol, and allows you to transfer files to and from a remote network host. This article necessarily cannot serve as an exhaustive description of the "anonymous FTP" process. (In fact, the Unix "ftp" program is only one of many user interfaces to the INTERNET FTP.) However, in Part I I will give an example of a typical Unix FTP session, and I will list the addresses of a few archive sites for Macintosh and MS-DOS software. Next month, in Part II, I will describe some of the techniques for decoding and downloading this software to your microcomputer. FTP is a privilege granted to users of the INTERNET by the administrators of sites containing these archives. Please try to restrict your file transfers to non-business hours, because you and other FTP users can cause the host computer to slow down significantly. In addition, please minimize the time that you are connected to the remote site so that others may take advantage of the opportunity. A screen capture of a typical (brief) FTP session is shown in Fig. 1. From a Unix machine at the University of Washington ("milton"), I connected to sumex- aim.stanford.edu, where a large collection of Macintosh software is archived. The numbers in parentheses located on the left margin of Fig. 1 correspond to the annotations listed below. (1) At your Unix prompt, enter "ftp" followed by a space and either the name or the numerical INTERNET address of the remote host. Occasionally, a host will accept only the INTERNET address. If the remote site is active, then you will be connected to the remote FTP server. (2) When the remote machine asks for your name, enter "anonymous." Some hosts limit the number of off-site FTP users; if the number of connections has already reached the maximum, you will be asked to try again later. (3) For your password, you are generally asked to enter your e-mail address, such as "beausol@u.washington.edu," followed by a return. However, some systems will permit you to enter virtually any text instead. (4) After these preliminaries, you will enter your local Unix "ftp" command interpreter, which will provide you with the "ftp>" prompt. Usually, you will first be logged in to a "root directory" that has been set aside for FTP purposes by the system administrators; you must then navigate to the archive itself. At sumex-aim.stanford.edu, the Macintosh software archive is located in the directory "info-mac." You can change the current working directory on the remote host using the "cd" command. In the example of Fig. 1, I have also moved to the subdirectory "util" on the info-mac directory. Whenever you have finished with a particular subdirectory, enter "cdup" at the "ftp>" prompt to move up one directory level. (5) Enter "get" followed by a space and the name of the file to be transferred. The file will then be copied to your local Unix directory. In the example of Fig. 1, the ".hqx" extension indicates that the Macintosh file has been encoded as purely ASCII characters using BinHex (discussed in more detail in Part II.) Usually, ASCII is the default FTP transfer mode. However, if the file has been archived in binary format, then at the "ftp>" prompt, and prior to transferring the file, you must enter "binary." Sometimes, if the file is large and the remote system is busy, the transfer may take considerable time. To keep an eye on the progress of the transfer, enter "hash" before getting the file; then as each 1024-byte block of data is transferred, a "#" hash mark will be printed on your monitor. If you would like to see an abbreviated list of the files contained in the current directory, enter "ls"; for a more verbose list that includes information about each file's size and the date that it was archived, enter "dir" followed by a carriage return. (6) When you are finished transferring the files you need, be courteous and log off of the remote machine as quickly as possible. At the "ftp>" prompt, enter either "by" or "qui." These are the most basic commands that you will use during any FTP session. You can usually find a complete description of the FTP command interpreter used at your Unix site by viewing the "manual pages" (i.e., by entering "man ftp"). There are a number of archives of software for the Macintosh, IBM PC and compatibles, and other popular personal computers. In Table I, I have listed the name of the host, the Internet address, the directory containing the archive, the microcomputer, and the appropriate transfer mode for some of the most popular archives. (Of course, virtually all documentation files are stored as pure ASCII.) One of the largest and most frequently updated Macintosh software archives is maintained at sumex-aim.stanford.edu. I recommend that the inexperienced user explore the subdirectory /info-mac/help. OzTeX, the free Macintosh implementation of TeX mentioned by Tony Siegman in last month's column, may be found at midway.uchicago.edu (University of Chicago); it is quite large, so be prepared! The MS-DOS archive at wsmr-simtel20.army.mil (White Sands Missile Range) is enormous, but it is difficult to navigate because the host does not use Unix. Nevertheless, there are a number of text documents in the root directory that describe the FTP commands for the simtel20 server. A Unix mirror of the simtel20 archive is maintained at wuarchive.wustl.edu (Washington University at St. Louis); if you are new to FTP on the IBM PC, then an excellent place to begin is the wuarchive subdirectory /mirrors/msdos/starter. The best way to learn more about FTP and other microcomputer archives is to subscribe to the appropriate INTERNET news groups. A full description of INTERNET news groups is beyond the scope of this article; you'll need to list the manual pages for your system news reader or to contact your local system administrator to get started. However, news groups of interest to microcomputer users have names that begin with prefixes like "comp.sys.mac..." and "comp.sys.ibm.pc..." In particular, the news groups "comp.sys.mac.digest" and "comp.sys.ibm.pc.d" describe in detail new additions to the archives at sumex- aim and simtel20, respectively. The precise implementation of FTP is site-dependent, so "your mileage may vary." But the basics of file transfer are usually easy to master and are well worth the effort. Next month, I will describe the basics of decoding and downloading files obtained via FTP. (I am grateful to Geoff Kinnel, Betsy Richards, Geoff Allen, and Jim Matthews for their generous assistance in gathering information for this article.) (C) Copyright 1991 Raymond G. Beausoleil Figure 1: Screen Capture of an ftp session. (1) milton> ftp 36.44.0.6 Connected to 36.44.0.6. 220 sumex-aim FTP server (SunOS 4.0/3) ready. (2) Name (36.44.0.6:beausol): anonymous 331 Guest login ok, send mail address (user@host) as password. (3) Password: 230 Guest connection 7 (of 25) accepted, access restrictions apply. (4) ftp> cd /info-mac/util 250 CWD command successful. (5) ftp> get unstuffit-deluxe-20.hqx 200 PORT command successful. 150 ASCII data connection for unstuffit-deluxe-20.hqx (128.95.136.1,11969) (172867 bytes). 226 ASCII Transfer complete. local: unstuffit-deluxe-20.hqx remote: unstuffit-deluxe-20.hqx 175534 bytes received in 7.2 seconds (24 Kbytes/s) (6) ftp> by 221 Goodbye. Table I: Site Name IP Address Directory Software Mode ------------------------------------------------------------------------ sumex-aim.stanford.edu 36.44.0.6 /info-mac Mac ASCII midway.uchicago.edu 128.135.12.73 /pub/OzTeX/oztex Mac Binary wsmr-simtel20.army.mil 26.2.0.74 Non-Unix! MS-DOS Binary wuarchive.wustl.edu 128.252.135.4 /mirrors/msdos MS-DOS Binary --------------------------------- End of Part I ------------------------------ ----------------------------- Beginning of Part II --------------------------- An FTP Primer II: Downloading and Decoding Ray Beausoleil beausol@u.washington.edu Last month, in Part I of this article, I briefly described the INTERNET File Transfer Protocol (FTP). In particular, I demonstrated how to use the Unix "ftp" interface to transfer personal computer software packages from a remote archive to your local Unix mainframe or minicomputer. These programs have usually been compressed and/or encoded by the archive administrators. This month, I will provide a brief introduction to the process of first downloading this software to your microcomputer, and then decoding it using special utility programs. The method that you must use to download software from your local mainframe computer to your microcomputer depends on the operating system and the software installed on the mainframe, and on the configuration of your network (e.g., Ethernet or modem). You should begin by asking your system administrator for a list of information transfer protocols that have been installed at your site and the commands that invoke these protocols. Some of the most popular protocols include XModem, YModem, ZModem, and Kermit. Paul Kelley has described XModem and Kermit in his article "Information transfer for personal computers," published in the February 1991 edition of this column. In Tables I and II, I have listed freeware and shareware telecommunications and utility software packages for the Macintosh and the IBM PC, respectively. For Macintosh software, I recommend the archive at sumex-aim.stanford.edu (INTERNET address 36.44.0.6), located in the directory "/info-mac". ZTerm, an excellent shareware telecommunications application program, can be found in the directory "/info-mac/comm". ZTerm not only uses the XModem and YModem data transfer protocols, but also offers one of the best implementations of the ZModem protocol for any personal computer. When you are connected through ZTerm to a Unix mainframe that uses the ZModem protocol, you may download a file simply by entering "sz" followed by a space and the name of the file. ZTerm detects that a file is being sent, identifies the file type, and then chooses the correct transfer mode! For local systems which have implemented the Kermit protocol, the program MacKermit (also available at sumex-aim.stanford.edu in the "/info-mac/comm" directory) provides a robust Macintosh interface. A huge archive of IBM PC software is maintained at wuarchive.wustl.edu (INTERNET address 128.252.135.4), in the directory "/mirrors/msdos". The most popular shareware telecommunications package for the IBM PC, ProComm, may be found there in the subdirectory named (oddly enough) "procomm". ProComm uses the XModem, YModem, and Kermit transfer protocols, and can also follow the ZModem protocol through an external command shell using the transfer program "DSZ.COM", which should be placed in the same MS-DOS directory as the ProComm program itself. After connecting to your local Unix mainframe through ProComm, enter "sz" followed by a space and the name of the file to be downloaded. Then, through ProComm, enter the MS-DOS gateway (the "DOS shell") and input "dsz rz" at the MS-DOS prompt. After the file has been written to your personal computer's disk, simply enter "exit" at the DOS prompt to return to ProComm. As Paul Kelley mentioned in his article, the simplest way to download files to your microcomputer is to display the file on your monitor. Both ZTerm and Procomm allow you to capture incoming text and write the text to a disk file. As described below, you may then decode the files for later use. Almost all of the files stored in the large archive of Macintosh software maintained at sumex-aim.stanford.edu have been encoded as ASCII (text) characters using a format known as BinHex 4. These files have names that end with the extension ".hqx", and can be captured directly from your monitor after you have transferred them to your local Unix host. You may direct a Unix machine to write a ".hqx" file to your monitor by entering the command "cat", followed by a space and the name of the file to be transferred. However, almost all of the files stored in the IBM PC software archive wuarchive.wustl.edu have been stored in binary format. After you have transferred one of these files (e.g., "file.arc") to your local Unix mainframe or minicomputer, you can use the command "uuencode file.arc file.arc" to ASCII-encode "file.arc" and then write it to your monitor. In both cases, you must decode the ASCII file on your microcomputer using one of the utility programs listed in Tables I and II; since you will not be able to decode these utilities themselves until after you have the utilities, you must obtain copies of their binary executable files from a colleague or user group. A typical binary file can be up to 50% smaller than the corresponding encoded ASCII file, and can be transferred to your personal computer in proportionally less time. Therefore, if at all possible, you should try to download using the binary transfer mode. This is relatively straightforward for IBM PC files transferred from the wuarchive.wustl.edu archive and then downloaded to a microcomputer using ProComm Plus. You may decode BinHex Macintosh files into MacBinary files on your local Unix host prior to downloading them using a utility such as "mcvert." You may build your own copy of "mcvert" by following these steps: (1) transfer the file "mcvert-15.shar" from the "/info-mac/unix" subdirectory at sumex- aim.stanford.edu using "ftp"; (2) enter "sh mcvert-15.shar" at your local Unix prompt, and ignore any error messages caused by the file header; and (3) enter "make" at the Unix prompt. This process will create a number of files on your directory; you may delete all but "mcvert" itself. Now, to decode any files that have the extension ".hqx" (including files that consist of more than one part), simply enter "mcvert *.hqx" at the Unix prompt. Your Unix directory will then contain files with the extension ".bin", which can be downloaded using the MacBinary transfer mode. Both the Macintosh and the IBM PC binary files that you have downloaded to your personal computer are actually miniature archives that contain one or more compressed executable and/or data files. These archives can be easily and rapidly expanded using the appropriate utility files listed in Tables I and II. (The label "sea" designates self-extracting archives which will decompress themselves automatically upon launching.) On the Macintosh, files obtained from sumex-aim.stanford.edu will usually have extensions such as ".sit" (Stuffit Classic), ".cpt" (Compact Pro), or ".sea" (Compact Pro self-extracting archive). On the IBM PC, files transferred and downloaded from wuarchive.wustl.edu will have extensions such as ".ARC" (PKUNPAK.EXE), ".ZIP" (PKUNZIP.EXE), ".LHZ" (LHARC.EXE), ".ZOO" (LOOZ210.EXE), or ".EXE" (self- extracting archive or simple executable file). At first, the downloading and decoding process may seem daunting to you, particularly if either the system architecture of your local host is not Unix, or the software installed on that system does not follow one of the few examples that I have given in this article. Rest assured that others have almost certainly solved your problems already; one of your most dependable resources is the knowledge of your colleagues. Alternatively, as I mentioned briefly in Part I, you may learn more about personal computer telecommunications by subscribing to the appropriate INTERNET news groups. If you ask the right people the right questions, you might find that while you may not be able stand upon the shoulders of giants, you may be able to stand upon their feet. (I am grateful to John McGarvey, Matt Derstine, Geoff Kinnel, Betsy Richards, David Faust, and Geoff Allen for their generous assistance in gathering information for this article.) (C) Copyright 1991 Raymond G. Beausoleil Table I: Files obtained from sumex-aim.stanford.edu (36.44.0.6) in the directory /info-mac (ASCII Transfer Mode) File Name Location Description ----------------------------------------------------------------------- file-types.txt help Brief list of sumex-aim file types zterm-085.hqx comm ZTerm (X,Y,ZModem; no Kermit) mackermit-098.hqx comm MacKermit (No X,Y,ZModem) stuffit-16-part1.hqx util Stuffit Classic w/BinHex 4 (sea) stuffit-16-part2.hqx util compact-pro-13.hqx util Compact Pro w/BinHex 4 (sea) mcvert-15.shar unix Unix shell archive for mcvert Table II: Files obtained from wuarchive.wustl.edu (128.252.135.4) in the directory /mirrors/msdos (Binary Transfer Mode) File Name Location Description ----------------------------------------------------------------------- 00-files.doc starter Description of wuarchive file types 00-index.txt starter Descriptions of files in /starter prcm243.arc procomm ProComm shareware communications program prcm243d.arc procomm ProComm documentation prcm243d.arc procomm ProComm utilities dsz0404.zip zmodem DSZ.COM (ZModem for ProComm) pk361.exe starter PKPAK.EXE/PKUNPAK.EXE (sea) pkz110eu.exe starter PKZIP.EXE/PKUNZIP.EXE (sea) lh113c.exe starter LHARC.EXE (sea) looz210.com starter ZOO archive extracter/lister uudecode.com starter Convert ASCII uuencoded files to binary --------------------------------- End of Part II -----------------------------.