8. NETWORKING. 8.1 Introduction

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1 38 8. NETWORKING 8.1 Introduction A network connects computers to each other and allows them to communicate with each other. The Physics Department computer system is connected with two different networks. The ethernet connects the UNIX workstations to each other and to the terminal server. Most Macintoshes and PC's are also on the ethernet. The localtalk network connects some Macintoshes and various printers. The two networks communicate with each other as well, through a network bridge that takes information from each network and converts it to information understandable by the devices on the other network. Thus, a microcomputer on localtalk network can access an SGI on ethernet, while a user on an SGI workstation can transfer files from a Macintosh. Of course, it's not quite that simple: you don't just connect two computers with very different CPU s and operating systems and expect them to communicate. To communicate, some sort of common language is needed. In networking, these languages are called protocols. Our network "speaks" two protocols: Appletalk and TCP/IP. The protocols are implemented as software programs running on each device on the network. The uses for these various "languages" are discussed briefly below. If it's beginning to seem that networking is fairly complicated, you are correct, partly due to the wide variety of devices and applications available, and partly because historically, each manufacturer wrote its own protocol. There are more complications: The Physics Department's ethernet is bridged to the campus network, ISUnet, which is higher speed ethernet network running on fiber optic hardware. Other departments have ethernet and localtalk, using a variety of protocols. Moreover, ISUnet is connected to the international Internet network (running TCP/IP) which is connected to hundreds of different types of computers around the country and world! As you can imagine, getting all these computers to communicate would be impossible without some standard, common protocol. It turns out that the TCP/IP protocol is the de facto standard, and software to run it is available on essentially every commonly used computer. That's why all the computers in the physics network speak TCP/IP. So why do we need anything else? As mentioned above, partly for historical reasons, but also because other protocols are better for some tasks. Consider Appletalk: Appletalk was developed to make small networks simple. It's much easier to use and set up for a novice user than TCP/IP - particularly for the common tasks of printer and file sharing. So all Apple devices speak Appletalk. It is when you want different brands or types of computers to speak to each other that you need the standard TCP/IP. Thus, we use both protocols in the department. The most basic type of communication between computers involves remote login, file transfer, electronic mail, printer sharing, and file sharing. Each protocol implements these basic features and more. We will discuss some of these here, and come back to discuss more advanced features in a later chapter. 8.2 TCP/IP Commands on UNIX The TCP/IP protocol provides access to the Internet, an international collection of computer networks connecting nearly all the national laboratories, major universities, and corporate research institutions. Remote logins and file transfers are accomplished with the SSH and SFTP (and their predecessors TELNET and FTP) commands, respectively. Additional features, including electronic mail and an international bulletin board, are also available.

2 Remote Login using SSH The TELNET command is analogous to dialing a telephone. Each device on the network has a "phone number" called an IP address or IP number: usually four 3-digit numbers separated by periods. Most devices also have more mnemonic names ("host names") which correspond to the IP numerical address. For example, some campus IP addresses are: Computer Host name IP address Physics Dual G4 meitner.phy.ilstu.edu Physics Mac file server macserver.phy.ilstu.edu Note that all these computers have the same first two numbers and the same last two words. That is because they are all at ISU (code name ILSTU, number ) which is an educational institution (code name EDU, various numbers). Other types of institutions on the national Internet are government (GOV), commercial (COM), and military (MIL). Thus a computer at a NASA laboratory is NSSDCA.GSFC.NASA.GOV, for example. Any computer on the network for which you have a signon, you can get to with the SSH or TELNET commands: SSH user@hostname or telnet hostname If you type this command on a Unix machine and wait a few seconds during which the two computers exchange information, you should see the login banner for the desired host computer. For example SSH user@ will get you on the G4 ("Meitner"). Try it File Transfer To transfer files under TCP/IP you use the ftp command (for File Transfer Protocol) in the same way: ftp hostname or ftp IP address After connection you will be prompted for the account you wish to use on the remote machine, after which the host system will usually ask for the password for the account. To transfer an ASCII file from the remote host to your computer use the ftp GET command: get filename and to transfer from your machine to the remote computer, use the ftp PUT command: put filename Binary images may be transferred using the ftp IMAGE command: image put filename Help is usually available at the FTP prompt by typing HELP.

3 40 Many systems have "guest" logins to allow remote users to FTP files that are available to the public. In this way they don't have to give out real logins to everyone. The standard format for guest logins is with the username ANONYMOUS, using your actual username or electronic mail address as a password. Guest accounts usually have absolute minimum privileges to discourage hacking. Interesting places to look include: UUNET.UU.NET UIARCHIVE.CSO.UIUC.EDU WUARCHIVE.WUSTL.EDU (UNIX software) (Macintosh and PC software) (Too much available to list) Anonymous FTP is a useful resource, since much useful software is out there. Since the resources available are growing almost daily, the system managers still have much to learn about what resources are available and how to access them. Other resources on Internet include various databases, library computers, notes files, etc. If you learn of useful Internet resources, feel free to send to root Electronic Mail Electronic mail may be transferred between the Physics Department and any other host on the Internet using the ELM mail exchange software from Worcester Polytechnic Institute and Xerox. Use of this software should be straightforward if the user is already familiar with the basic use of the Jove editor (see chapter 3). As an example, suppose you wanted to send a message to a co-worker whose login name is JOEUSER on the machine NSSDCA.GSFC.NASA.GOV. You would enter ELM, and at the menu type the letter 'm' (short for "mail"). (If this is your first ELM session, you may be asked whether the program should build a Mail directory for you - you should answer "yes".) The ELM program will then ask you who to send the note to, and also for a short summary. To: joeuser@nssdca.gsfc.nasa.gov Subject: I'm lost... Once you have provided those, you will be placed into the JOVE editor to type the body of your letter. You may use any of the normal Jove commands to prepare your message (this includes using CTRL-X CTRL-I to insert the contents of another file into your message). I used FTP to obtain your program SPIN.F last night, but I don't understand how to use it. What parameters do I need to supply? Bill When you are finished typing, save your work and exit JOVE as usual. ELM will ask you to confirm that the letter is ready to send. If you answer "s", the letter will be sent. 8.3 TCP/IP Commands on the Macintosh The Appletalk protocol provides several services unique to Apple Macintosh compatible computers, such as the basic functions of printer sharing, and file serving. Remote login and UNIX file transfer are accomplished with the SSH and FETCH programs, respectively, which use the TCP/IP protocol. Additional features, including electronic mail and the international USENET bulletin board, are also available Remote Login using SSH The Macintosh SSH command is identical to its UNIX cousin described above. Like other Unix applications that have found a home on Mac OSX, you start the program by double-clicking the mouse on the Terminal utility icon. Then you follow the same procedure as above.

4 41 From then on, the Mac s Terminal window will act like a terminal attached to the remote Unix host. You may log in, edit programs, run jobs, or perform any of the normal functions you would do from a terminal. You may even open several such connections at once, either to the same machine or different machines File Transfer using Dartmouth Fetch Dartmouth University's Fetch is a FTP client program for the Macintosh. It combines the versatility of its Unix cousin with the comfortable Mac point-and-click user interface. It is most often used either to copy Unix text files to floppy disks for home use or to copy Unix data files to a local Mac disk for later use by a Mac analysis program such as Kaleidagraph. When Fetch starts up it will ask you for four pieces of information: the machine you wish to connect to, the login name to use on that machine, the password to use, and optionally the name of a subdirectory to start out in. Usually you will use "meitner.phy.ilstu.edu" for the machine name, your regular login name and password, and leave the Directory space blank. Use the mouse or the TAB key to switch from field to field, not the RETURN key. When the information is just right, click on the OK button or press RETURN. Fetch will then make an FTP connection to Meitner. You will see a listing of all your files in the window. To download a file to the Mac, just select it by clicking on the filename, and click on the "Get File" gadget. Fetch will prompt you for the right place to put the file on the Mac. This is a standard Mac requestor; you simply navigate it to the right disk or folder The Macintosh File Server While each Macintosh has its own copy of some of the most commonly used applications, there are more applications available on the Physics Department's AppleShare file server. Connect to the AppleShare file server by selecting the Chooser from the Apple menu. The Chooser is used both for network file serving and for network printers. By clicking the mouse on the AppleShare icon in the Chooser, you will be shown a list of all visible servers. You should select "Mac Server" and click on the OK button. The Chooser will then give the option of using Guest access or providing a login name and password to use. You should click on the Guest access button. The Chooser will finally ask you which disk on the server you wish to access. You should normally select the "Physics FTP Server". The disk should appear on your Macintosh desktop just as though it was a directly attached disk. Don't forget to close the Chooser when you are done by clicking the close gadget in the upper lefthand corner of the window. Using the file server is just like using another hard disk. Programs may be used simply by double-clicking the mouse on their icons. Several applications (spreadsheets, graphics, etc.) are available to run directly from the server. In addition, many freeware utilities are available for downloading to your floppies. Feel free to explore. When you are done using the server, you should always disconnect from it by dragging the server disk icon to the trashcan. Don't leave yourself connected Electronic Mail using Eudora Users who prefer the comfortable Macintosh interface may prefer to handle all their electronic mail on a Macintosh. Towards this end, we recommend using Eudora.

5 42 Eudora can either keep incoming and outgoing mail your department account, and only contact the mail server to actually send and receive new mail, or it may use the IMAP protocol to permanently keep mail on the server. We can help you configure yours properly. See Dr. Bogue if you are interested, or sign up for one of the free mini-classes in Julian Hall. The complete set of Eudora features, including a brief tutorial, is described in the Eudora manual on the bookshelf in room Electronic News using MT-NewsWatcher Users who are interested in the international Usenet bulletin board may be interested in using MT- NewsWatcher on the Macintosh. In order to run in a "Lab" environment, MT-Newswatcher will need to keep your personal information in your departmental account. Be sure you are using it. You will be prompted for a few pieces of information (such as the IP name of the news server machine "news.ilstu.edu", your favorite machine to handle "mail.phy.ilstu.edu", and your address). MT-NewsWatcher will then open two windows. One will contain the full list of all available news groups, while the other contains a list of those newsgroups which you currently subscribe to (i.e., none). To subscribe to a group (we suggest trying sci.physics), just find it in the full list, click on it with the mouse, and drag it to the other window while holding the mouse button down. To read articles in a group, just double-click on the group name in the subscribed list. When you are done reading news, you will want to save your subscription list onto your floppy. Just choose "Save" from the "File" menu. When you resume reading news, you may start NewsReader by double-clicking on your saved subscription list document The World-Wide Web It's been in Time Magazine and the Congressional Record, and it's even at ISU. Web client programs are available on most Physics Macintoshes. These comments apply to all major web browsers, including Safari, Mozilla, and MSIE. The Web actually consists of thousands of computers on the Internet, linked together by TCP/IP and two further protocols called HTTP and HTML. Each provides a small amount of information on a topic of their choice, related materials such as pictures or movie clips, and any number of links to other computers on the Web containing related information. If you know which site you want to access, you may select "Open Location" from the File menu and type it in (try " for example). If not, you should start at the Physics Department HTML home page (loaded by default). Links to other sites are highlighted in blue. Just click on the link to access it. Warning: Surfing the web can be habit-forming!

JCCC Virtual Labs. Click the link for more information on installing on that device type. Windows PC/laptop Apple imac or MacBook ipad Android Linux

JCCC Virtual Labs. Click the link for more information on installing on that device type. Windows PC/laptop Apple imac or MacBook ipad Android Linux JCCC Virtual Labs Revision 9/21/2017 http://ats.web. Welcome to the JCCC Virtual Lab Environment. This system allows students to access campus software titles on their personal computers from almost anywhere.