Learning DebianGNU Linux-Chapter 11. Getting Connected to the Internet

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Learning DebianGNU Linux-Chapter 11. Getting Connected to the Internet11. Getting Connected to the InternetThis chapter explains how to use Linux to connect to remote servers. First, itexplains how to use wvdial, a program that makes it easy to connect to theInternet via a PPP connection provided by an ISP. Then, the chapter explainsbasic TCP/IP network concepts that you must know in order to administer aLinux system connected to the Internet or a local area network. So that youcan use your knowledge of TCP/IP effectively, the chapter explains how touse pppconfig to configure and administer a system that connects to alocal area network and to a remote server via PPP. Next, the chapterdescribes several popular network client applications available under Linux,including a web browser and an FTP client. The chapter then describes theuse of minicom and seyon, which provide dial-out capabilities like thoseof Windows hyperterminal. Finally, the chapter shows how to make aPPP connection manually, by using minicom.11.1 Connecting to the InternetMost Internet service providers (ISPs) offer two primary types of service:shell accounts and PPP (point-to-point protocol) accounts. Shell accountswere more popular before the advent of the Web. A shell account lets youuse your computer much as if it were a virtual console associated with aremote computer. You can type commands, which are interpreted by theremote computer, and view the resulting output on your computer. Althougha few web browsers, such as Lynx, can operate via a shell account, theydont generally support the highly graphical, multimedia pages which websurfers have come to expect.In contrast, a PPP account connects your computer directly to the Internet.While your computer is connected to the Internet, you can use it to surf theWeb with your favorite browser. If your ISP allows, you can even run a webserver, providing pages that can be viewed by others around the world.You can compare the two types of Internet accounts - shell and PPP - withtwo kinds of postal service. Imagine that no mail carrier actually comes toyour home to pick and deliver mail. Instead, every time you want to conductpostal business, you go to the post office. This resembles a shell account:The computer that connects you to the Internet is remote, and every time youwant to do something on the Internet you must open a terminal, or telnet,session to that computer. PPP, on the other hand, is like home delivery: TheInternet comes right to your doorstep, and your computer is literally placedon the Internet by the machine at your ISP that you connect to.Under Microsoft Windows, you use hyperterminal to access a shellaccount and Dial-Up Networking to access a PPP account. Under Linux, youcan choose from among several programs that let you access a shell account.The most commonly used programs are minicom and seyon. To access aPPP account under Linux, you use the PPP daemon, pppd. The next sectiondescribes how to use wvdial to make the process of establishing a PPPconnection simple.11.2 Configuring Your ModemYour modem is a peripheral device to Linux, like a CD-ROM drive, harddrive, or a mouse. Your modem will be connected to a serial port, whichmeans that one of the serial devices in the /dev directory actually points toyour modem. You may notice that theres also a file, /dev/modem, whichserves as a placeholder for your modem. Initially this file doesnt point toanything. To simplify your operations, so that applications likeminicomand seyon need only refer to /dev/modem, you can create asymbolic link from the serial device connected to your modem to/dev/modem.To do so, login as root and issue the command:ln -sf /dev/ttySX /dev/modemwhere X is replaced by the number corresponding to the serial device thatpoints to your modem. Table 11.1 shows how the proper commandcorresponds to the device by which your modem is known user DOS andLinux. Table 11.1: Command to Create /dev/modemDOS Modem Linux Modem CommandDevice Device Table 11.1: Command to Create /dev/modemDOS Modem Linux Modem CommandDevice DeviceCOM1 ttyS0 ln -sf /dev/ttyS0 /dev/modemCOM2 ttyS1 ln -sf /dev/ttyS1 /dev/modemCOM3 ttyS2 ln -sf /dev/ttyS2 /dev/modemCOM4 ttyS3 ln -sf /dev/ttyS3 /dev/modem11.3 Using wvdialISPs use a variety of dialogs to make a PPP connection. Often the mostdifficult part of configuring your computer to make a PPP connection isspecifying dialog options consistent with those required by your ISP, ...