Chapter 14: Web, FTP, and Java Clients

Overview

Most Linux distributions will provide powerful Web and FTP clients for accessing the Internet. Many are installed automatically and are ready to use when you first start up your Linux system. Linux also includes full Java development support, letting you run and construct Java applets. This chapter will cover some of the more popular Web, Java, and FTP clients available on Linux.

Web and FTP clients connect to sites that run servers, using Web pages and FTP files to provide services to users. Sites are accessed using their Internet addresses. Local networks use the same addressing format. Though discussed in more detail in Chapter 38, a quick review is provided here. The Internet uses a set of network protocols called TCP/IP, which stands for Transmission Control Protocol/Internet Protocol. In a TCP/IP network, messages are broken into small components called datagrams, which are then transmitted through various interlocking routes and delivered to their destination computers. Once received, the datagrams are reassembled into the original message. Datagrams are also referred to as packets. Sending messages as small components has proved far more reliable and faster than sending them as one large bulky transmission. With small components, if one is lost or damaged, only that component has to be resent, whereas if any part of a large transmission is corrupted or lost, the entire message must be resent.

On a TCP/IP network such as the Internet, each computer is given a unique address called an IP address. The IP address is used to identify and locate a particular host—a computer connected to the network. To make identifying a computer on the Internet easier, the Domain Name Service (DNS) was implemented. The DNS establishes a domain name address for each IP address. The domain name address is a series of names separated by periods. Whenever you use a domain name address, it is automatically converted to an IP address, which is then used to identify that Internet host. The domain name address is far easier to use than its corresponding IP address.

A domain name address needs to be registered with an Internet domain name registry such as the American Registry for Internet Numbers (ARIN) so that each computer on the Internet can have a unique name (see www.iana.org for more information). Creating a name follows specified naming conventions. The domain name address consists of the hostname, the name you gave to your computer; a domain name, the name that identifies your network; and an extension that identifies the type of network you are on. Here is the syntax for domain addresses:

host-name.domain-name.extension

In the following example, the domain address references a computer called metalab on a network referred to as unc. It is part of an educational institution, as indicated by the extension edu.

metalab.unc.edu

With the whois command, you can obtain information for domain name servers about different networks and hosts connected to the Internet. Enter whois and the domain name address of the host or network, and whois displays information about the host, such as the street address and phone number, as well as contact persons.

$ whois domain-address