FTP

The ability to transfer data between computers is central to the inter-networking concept. TCP/IP implements computer-to-computer data transfers thorough FTP (File Transfer Protocol).
An FTP session involves first connecting to and signing on to an FTP server somewhere on the Net. Most public FTP sites allow anonymous FTP. This means you can sign in with the user name anonymous and use your e-mail address as your password. However, some sites are restricted and require the use of an assigned user name and password.
Once in, you can list the files available on the site and move around through the directory structure just as though you were on your own system. When you've found a file of interest, you can transfer it to your computer using the get command (or mget for multiple files). You can also upload files to an FTP site using the put command.
The FTP process was originally designed for text-only UNIX shell style systems. But today, there are many FTP programs available that go way beyond the original FTP capabilities, adding windows, menus, buttons, automated uploading and downloading, site directories, and many more modern amenities.

Individual files on an FTP site are handled according to the way they are defined in your browser's configuration setup, just as though you were browsing a Web site. For example, if you're exploring an FTP site and click the link for a .gif picture file, it will be displayed in the browser window. Text files and HTML encoded files will be displayed too. If you have configured helper applications for sound or video, clicking these types of files will display them using the configured helper applications. Clicking an unconfigured file type will generally bring up a requester asking you to configure a viewer or save the file to disk.
Since you most often want to save files to disk from an FTP site, not view them, you can generally get around all this by using the browser's interactive option to save a file rather than display it. For example, in Netscape you can choose to save a file rather than view it by simply holding down the Shift key before clicking the file's link. 

Telnet

One of the driving forces behind the development of ARPAnet was the desire to afford researchers at various locations the ability to log on to remote computers and run programs. At the time, there were very few computers in existence and only a handful of powerful supercomputers (though the supercomputers of the early 1970s were nowhere near as powerful as the desktop machines of today).
Along with e-mail, remote logon was one of the very first capabilities built into the ARPAnet.
Today, there is less reason for logging on to a remote system and running programs there. Most major government agencies, colleges, and research facilities have their own computers, each of which is as powerful as the computers at other sites.
TCP/IP provides a remote logon capability through the Telnet protocol. Users generally log in to a UNIX shell account on the remote system using a text-based or graphics-based terminal program. With Telnet, the user can list and navigate through directories on the remote system and run programs.
The most popular programs run on shell accounts are probably e-mail programs, such as PINE; Usenet news readers, such as nn or rn; and text editors, such as vi or Emacs. Students are the most common users of Telnet these days; professors, scientists, and administrators are more likely to have a more direct means of access to powerful computers, such as an X Windows terminal.
Most Web browsers don't include built-in Telnet capabilities. Telnet connections are usually established using a stand-alone terminal program, such as that shown in figure 1.4. These programs can also be used by those who want Telnet capabilities on the Web by configuring them as browser helper applications. 

TCP/IP

By the mid-1970s, many government agencies were on the ARPAnet, but each was running on a network developed by the lowest bidder for their specific project. For example, the Army's system was built by DEC, the Air Force's by IBM, and the Navy's by Unisys. All were capable networks, but all spoke different languages. What was clearly needed to make things work smoothly was a set of networking protocols that would tie together disparate networks and enable them to communicate with each other.
In 1974, Vint Cerf and Bob Kahn published a paper titled "A Protocol for Packet Network Internetworking" that detailed a design that would solve the problem. In 1982, this solution was implemented as TCP/IP. TCP stands for Transmission Control Protocol; IP is the abbreviation for Internet Protocol. With the advent of TCP/IP, the word Internet-which is a portmanteau word for interconnected networks-entered the language.
The TCP portion of the TCP/IP provides data transmission verification between client and server: If data is lost or scrambled, TCP triggers retransmission until the errors are corrected.

Note

You've probably heard the term socket mentioned in conjunction with TCP/IP. A socket is a package of subroutines that provide access to TCP/IP protocols. For example, most Windows systems have a file called winsock.dll in the windows/system directory that is required for a Web browser or other communications program to hook up to the Internet.

The IP portion of TCP/IP moves data packets from node to node. It decodes addresses and routes data to designated destinations. The Internet Protocol (IP) is what creates the network of networks, or Internet, by linking systems at different levels. It can be used by small computers to communicate across a LAN (Local Area Network) in the same room or with computer networks around the world. Individual computers connected via a LAN (either Ethernet or token ring) can share the LAN setup with both TCP/IP and other network protocols, such as Novell or Windows for Workgroups. One computer on the LAN then provides the TCP/IP connection to the outside world.
The Department of Defense quickly declared the TCP/IP suite as the standard protocol for internetworking military computers. TCP/IP has been ported to most computer systems, including personal computers, and has become the new standard in internetworking. It is the protocol set that provides the infrastructure for the Internet today.
TCP/IP comprises over 100 different protocols. It includes services for remote logon, file transfers, and data indexing and retrieval, among others.

Introducing the World Wide Web

Contrary to what the media would have you believe, the World Wide Web did not spring into being overnight. Though relatively new in human terms, the Web has a venerable genealogy for a computing technology. It can trace its roots back over 25 years, which is more than half the distance back to the primordial dawn of the electronic computing age.
However, the media is right in noting that the Web's phenomenal growth has so far outstripped that of any of its predecessors that, like a prize hog, it has left almost no room at the trough for any of them anymore. But like that prize hog, the Web is so much bigger and better and so much more valuable than the network technologies that preceded it, there is little reason to mourn the fact that they've been superseded.
In this chapter I'll discuss the history, development, and characteristics of the Web. You'll find out where it came from and what it's good for. If you're the impatient type and you just want to start using HTML to develop Web pages as quickly as possible, you can certainly skip this chapter and jump right in. However, as with all things, a little understanding of the background and underlying structure of the Web will not only enhance your enjoyment of and appreciation for what it is and what it can do, but it might even give you some insights into how to approach the development of your own Web sites.
The Web came out of the Internet, and it is both empowered and limited by the structure of the Internet. Today, most Web browsers include the capability to access other Internet technologies, such as Gopher, e-mail, and Usenet news, as well as the World Wide Web. So the more you know about the Internet as a whole, as well as the Web's place in it, the better you'll understand how to exploit the entire Net to its fullest potential.
Then, too, the Web and the Internet are more than just technology: they are an environment in which the members of an entire cyberculture communicate, trade, and interact. If you hope to establish your own Web site and make yourself a part of that culture, you'd better know what you're getting into. In a way, it's like moving to another country and trying to set up shop; if you don't speak the lingo and learn the customs, you'll never become a part of the community.
In this chapter, you learn about the following:

• A short history of the Internet, the home of the Web
• What Net technologies existed before the Web, and how they work alongside the Web today
• How to decipher Internet e-mail addresses and domain names
• How and why the Web sprang so suddenly into being
• How the Web has quickly grown to reign supreme on the Net
• What's on the Web and why you'll want to develop a presence there

The Genealogy of the Web

In the late 1950s, at the height of the Cold War, the Department of Defense began to worry about what would happen to the nation's communications systems in the event of an atomic war. It was obvious that maintaining communications would be vital to the waging of a worldwide war, but it was also obvious that the very nature of an all-out nuclear conflict would practically guarantee that the nation's existing communications systems would be knocked out.
In 1962, Paul Baran, a researcher at the government's RAND think tank, described a solution to the problem in a paper titled "On Distributed Communications Networks." He proposed a nationwide system of computers connected together using a decentralized network so that if one or more major nodes were destroyed, the rest could dynamically adjust their connections to maintain communications.
If, for example, a computer in Washington, D.C., needed to communicate with one in Los Angeles, it might normally pass the information first to a computer in Kansas City, then on to L.A. But if Kansas City was destroyed or knocked out by an A-bomb blast, the Washington computer could reroute its communications through, say, Chicago instead, and the data would still arrive safely in L.A. (though too late to help the unfortunate citizens of Kansas City).
The proposal was discussed, developed, and expanded by various members of the computing community. In 1969, the first packet-switching network was funded by the Pentagon's Advanced Research Projects Agency (ARPA).

So What's Packet Switching?

Packet switching is a method of breaking up data files into small pieces-usually only a couple of kilobytes or less-called packets, which can then be transmitted to another location. There, the packets are reassembled to re-create the original file. Packets don't have to be transmitted in order or even by the same route. In fact, the same packet can be transmitted by several different routes just in case some don't come through. The receiving software at the other end throws away duplicate packets, checks to see if others haven't come through (and asks the originating computer to try to send them again), sorts them into their original order, and puts them back together again into a duplicate of the original data file. Although this isn't the fastest way to transmit data, it is certainly one of the most reliable. Packet switching also enables several users to send data over the same connection by interleaving packets from each data stream, routing each to its own particular destination. Besides the original file data, data packets may include information about where they came from, the places they've visited in transit, and where they're going. The data they contain may be compressed and/or encrypted. Packets almost always also include some kind of information to indicate whether the data that arrives at the destination is the same data that was sent in the first place.

ARPAnet, as it was called, linked four research facilities: the University of California at Los Angeles (UCLA), the Stanford Research Institute (SRI), the University of California at Santa Barbara (UCSB), and the University of Utah. By 1971, ARPAnet had grown to include 15 nodes; there were a grand total of 40 by 1972. That year also marked the creation of the InterNetworking Working Group (INWG), which was needed to establish common protocols for the rapidly growing system.

Display Data from Mysql using Select Query in PHP Tutorial 93Hindi Urdu ...