To work with Internet and to utilize its facilities we use certain tools. For example,Telnet is a tool, which is utilized for logging on remote computers on the Internet. Let us briefly discuss about some of the important tools and services.
Domain name is a name given to a network for ease of reference. Domain refers to a group of computers that are known by a single common name. Somebody has to transfer these domain names into IP addresses. It is decided on the physical location of the web server as well as where the domain name is registered. Some generic domain names are:
Thus, humans use domain names when referring to computers on the Internet, whereas computers work only with IP addresses, which are numeric. DNS was developed as a distributed database. The database contains the mappings between the domain names and IP addresses scattered across different computers. This DNS was consulted whenever any message is to be sent to any computer on the Internet. DNS is based on the creation of the hierarchical domain based naming architecture, which is implemented as a distributed database. It is used for mapping host names and email addresses to IP addresses. Each organization operates a domain name server that contains the list of all computers in that organization along with their IP addresses. When an application program needs to translate a computer’s name into the computer’s IP address, the application becomes a client of the DNS. It contacts a domain name server and sends the server an alphabetic computer name then the server returns the correct IP address. The domain name system works like a directory. A given server does not store the names and addresses of all possible computers in the Internet. Each server stores the name of the computers at only one company or enterprise.
Most Internet protocols are specified by Internet documents known as a Request For Comments or RFCs. RFCs may be found at several locations on the Internet.
WWW is an Internet navigation tool that helps you to find and retrieve information links to other WWW pages. The WWW is a distributed hypermedia environment consisting of documents from around the world. The documents are linked using a system known as hypertext, where elements of one document may be linked to specific elements of another document. The documents may be located on any computer connected to the Internet. The word “document” is not limited to text but may include video, graphics, databases and a host of other tools.
The World Wide Web is described as a “wide area hypermedia information initiative among to give universal access to large universe of documents”. World Wide Web provides users on computer networks with a consistent means to access a variety of media in a simplified fashion. A popular software program to search the Web is called Mosaic, the Web project has modified the way people view and create information. It has created the first global hypermedia network.
Once again the WWW provides an integrated view of the Internet using clients and servers. As discussed earlier, clients are programs that help you seek out information while servers are the programs that find information to the clients. WWW servers are placed all around the Internet.
The operations of the Web mainly rely on hypertext as its means of interacting with users. But what is hypertext? Hypertext as such is the same as regular text that is it can be written, read, searched or edited; however, hypertext contains connections within the text to other documents. The hypertext links are called hyperlinks. These hyperlinks can create a complex virtual web of connections.
Hypermedia is an advanced version of hypertext documents as it contains links not only to other pieces of text but also to other forms of media such as sounds, images and movies. Hypermedia combines hypertext and multimedia.
In Internet there exists another way to meet people and share information. One such way is through Usenet newsgroups. These are special groups set up by people who want to share common interests ranging from current topics to cultural heritages. These are currently thousands of Usenet newsgroups.
The Usenet can be considered as another global network of computers and people, which is interwined with the Internet. However, Usenet does not operate interactively like the Internet, instead Usenet machines store the messages sent by users. Unlike mail from mailing lists, the news articles do not automatically fill your electronic mailbox. For accessing the information on newsnet, one needs a special type of program called a newsreader. This program help in retrieving only the news you want from Usenet storage site and display it on your terminal. Usenet is like living thing, New newsgroups gets added, the groups which have too much traffic get broken up into smaller specialized groups, the groups even can dissolve themselves. However, all of this occurs based on some commonly accepted rules and by voting. For Usenet, there is no enforcement body; it entirely depends on the cooperation of its computers owners and users.
The newsgroups are really meant fro interaction of people who share your interests. You can post your own questions as well as your answers to the questions of others, on the Usenet. One thing, which is worth mentioning here, is that when one is interacting wit people on Internet certain mannerism should be adopted. These rules are sometimes called “netiquette”. In a face-to-face conversation you can always see a person’s facial gestures and hand movements and can ascertain whether he is teasing or is being sarcastic or sometimes even lying. However, in on-line interaction one cannot see the person one is interacting with. The rules of netiquette may help to compensate some of these limitations of this on-line environment.
FTP (File Transfer Protocol), a standard Internet protocol, is the simplest way to exchange files between computers on the Internet. Like the Hypertext Transfer Protocol (Hypertext Transfer Protocol), which transfers displayable Web pages and related files, FTP is an application protocol that uses the Internet's TCP/IP protocols. FTP is commonly used to transfer Web page files from their creator to the computer that acts as their server for everyone on the Internet. It's also commonly used to downloading programs and other files to the computer from other servers. However, for such transfer you need an account name on a host and the password. The FTP program will make connection with the remote host, which will help you to browse its directories and mark files for transfer. However, you cannot look at the contents of a file while you are connected via FTP. You have to transfer the copy and then look at it once it is on your own account.
FTP includes many commands but only few are used to retrieve a file. A user needs to understand the three basic commands to connect to remote computer, retrieve a copy of file and exit the FTP program. The commands with their meanings are:
FTP service compress files to reduce the total amount of disk space the files require. Before transferring a file user must tell FTP that the file contains ASCII text or nontext file. FTP assumes to perform ASCII transfers unless the user enters the binary command.
There are many FTP programs that you can download from the Internet. Windows has its own command line based FTP program. To execute it, select Run from Windows taskbar and type FTP and press enter. By typing open command you can connect to any ftp server. To connect to FTP server you must have a login name and the password. Most of the FTP servers allow anonymous connections. In this case username is anonymous and password is your e-mail address.
Another important FTP program, which is available as a shareware, is WSFTP. Using this window based program it is easier to maintain your web site.
The working of TELNET,
The Pseudo-terminal driver program then hands over the commands or text to the operating system of the remote computer, which then invokes the application program on the remote server.
There are many databases available on the Internet. You can explore these databases using Telnet. There are going to be many Internet services yet to be created. Every year and better means of accessing the treasures of the Internet is appearing in which Telnet is the key for accessing.
Domain Name System
Domain name is a name given to a network for ease of reference. Domain refers to a group of computers that are known by a single common name. Somebody has to transfer these domain names into IP addresses. It is decided on the physical location of the web server as well as where the domain name is registered. Some generic domain names are:
| Domain name | Description |
|---|---|
| com | Commercial Organization |
| Edu | Educational Organization |
| Gov | Government Organization |
Thus, humans use domain names when referring to computers on the Internet, whereas computers work only with IP addresses, which are numeric. DNS was developed as a distributed database. The database contains the mappings between the domain names and IP addresses scattered across different computers. This DNS was consulted whenever any message is to be sent to any computer on the Internet. DNS is based on the creation of the hierarchical domain based naming architecture, which is implemented as a distributed database. It is used for mapping host names and email addresses to IP addresses. Each organization operates a domain name server that contains the list of all computers in that organization along with their IP addresses. When an application program needs to translate a computer’s name into the computer’s IP address, the application becomes a client of the DNS. It contacts a domain name server and sends the server an alphabetic computer name then the server returns the correct IP address. The domain name system works like a directory. A given server does not store the names and addresses of all possible computers in the Internet. Each server stores the name of the computers at only one company or enterprise.
SMTP and Electronic Mail
One of the very useful things about Internet is that it allows you almost instantly exchange of electronic message (e-mail) across the worlds. E-mail is a popular way of communication on the electronic frontier. You can E-mail to your friend or a researcher or anybody for getting a copy of a selected paper. Electronic mail system provides services that allowed complex communication and interaction. E-mail provide the following facilities:
Another commonly used Internet service is electronic mail. E-mail uses an application level protocol called Simple Mail Transfer Protocol or SMTP. SMTP is also a text-based protocol, but unlike HTTP, SMTP is connection oriented. SMTP is also more complicated than HTTP.
When you open your mail client to read your e-mail, this is what typically happens:
Similarly, when you send an e-mail message your computer sends it to an SMTP server. The server forwards it to the recipients mail server depending on the email address. The received message is stored at the destination mail server until the addressee retrieves it. To receive E-mail a user Internet account includes an electronic mailbox. A message sent for you is received at your Internet host computer, where it is stored in your electronic mailbox. As soon as you login into your Internet account, one of the first things you should do is to check your mailbox.
E-mail system follows the client-server approach to transfer messages across the Internet. When a user sends an E-mail message a program on the sender’s computer becomes a client. It contacts an e-mail server program on the recipient’s computer and transfers a copy of the message. Some of the mail programs those exist on Internet are UCB mail, Elm, Pine etc. However, one thing, which you must emphasize while selecting a mail program, is the user friendliness of that program. Through E-mail on Internet you can be in direct touch of your friend and colleagues.
Mailing lists on Internet
Another exciting aspect about the E-mail is that you can find groups of people who share your interests-whether you are inclined toward research, games or astronomy. E-mail provides a mechanism for groups of people who have shared interests to establish and maintain contact. Such interest groups are referred to as mailing lists (lists for short). After all they are mailing lists of the members e-mail addresses. You can subscribe to any of such lists. You will receive copies of all the mail sent to the list. You can also send mail to al subscribers of the list.
One of the most commonly used services on the Internet is the World Wide Web (WWW). The application protocol that makes the web work is Hypertext Transfer Protocol or HTTP. Do not confuse this with the Hypertext Markup Language (HTML). HTML is the language used to write web pages. HTTP is the protocol that web browsers and web servers use to communicate with each other over the Internet. It is an application level protocol because it sits on top of the TCP layer in the protocol stack and is used by specific applications to talk to one another. In this case the applications are web browsers and web servers.
HTTP is a connectionless text based protocol. Clients (web browsers) send requests to web servers for web elements such as web pages and images. After the request is serviced by a server, the connection between client and server across the Internet is disconnected. A new connection must be made for each request. Most protocols are connection oriented. This means that the two computers communicating with each other keep the connection open over the Internet. HTTP does not however. Before an HTTP request can be made by a client, a new connection must be made to the server.
When you type a URL into a web browser, this is what happens:
- Composing and sending/receiving a message.
- Storing/forwarding/deleting/replying to a message.
- Sending a single message to more than one person.
- Sending text, voice, graphics and video.
- Sending a message that interacts with other computer programs.
Another commonly used Internet service is electronic mail. E-mail uses an application level protocol called Simple Mail Transfer Protocol or SMTP. SMTP is also a text-based protocol, but unlike HTTP, SMTP is connection oriented. SMTP is also more complicated than HTTP.
When you open your mail client to read your e-mail, this is what typically happens:
- The mail client (Netscape Mail, Lotus Notes, Microsoft Outlook, etc.) opens a connection to it's default mail server. The mail server's IP address or domain name is typically setup when the mail client is installed.
- The mail server will always transmit the first message to identify itself.
- The client will send an SMTP HELO command to which the server will respond with a 250 OK message.
- Depending on whether the client is checking mail, sending mail, etc. the appropriate SMTP commands will be sent to the server, which will respond accordingly.
- This request/response transaction will continue until the client sends an SMTP QUIT command.The server will then say goodbye and the connection will be closed.
Similarly, when you send an e-mail message your computer sends it to an SMTP server. The server forwards it to the recipients mail server depending on the email address. The received message is stored at the destination mail server until the addressee retrieves it. To receive E-mail a user Internet account includes an electronic mailbox. A message sent for you is received at your Internet host computer, where it is stored in your electronic mailbox. As soon as you login into your Internet account, one of the first things you should do is to check your mailbox.
E-mail system follows the client-server approach to transfer messages across the Internet. When a user sends an E-mail message a program on the sender’s computer becomes a client. It contacts an e-mail server program on the recipient’s computer and transfers a copy of the message. Some of the mail programs those exist on Internet are UCB mail, Elm, Pine etc. However, one thing, which you must emphasize while selecting a mail program, is the user friendliness of that program. Through E-mail on Internet you can be in direct touch of your friend and colleagues.
Mailing lists on Internet
Another exciting aspect about the E-mail is that you can find groups of people who share your interests-whether you are inclined toward research, games or astronomy. E-mail provides a mechanism for groups of people who have shared interests to establish and maintain contact. Such interest groups are referred to as mailing lists (lists for short). After all they are mailing lists of the members e-mail addresses. You can subscribe to any of such lists. You will receive copies of all the mail sent to the list. You can also send mail to al subscribers of the list.
Http and World Wide Web
One of the most commonly used services on the Internet is the World Wide Web (WWW). The application protocol that makes the web work is Hypertext Transfer Protocol or HTTP. Do not confuse this with the Hypertext Markup Language (HTML). HTML is the language used to write web pages. HTTP is the protocol that web browsers and web servers use to communicate with each other over the Internet. It is an application level protocol because it sits on top of the TCP layer in the protocol stack and is used by specific applications to talk to one another. In this case the applications are web browsers and web servers.
HTTP is a connectionless text based protocol. Clients (web browsers) send requests to web servers for web elements such as web pages and images. After the request is serviced by a server, the connection between client and server across the Internet is disconnected. A new connection must be made for each request. Most protocols are connection oriented. This means that the two computers communicating with each other keep the connection open over the Internet. HTTP does not however. Before an HTTP request can be made by a client, a new connection must be made to the server.
When you type a URL into a web browser, this is what happens:
- If the URL contains a domain name, the browser first connects to a domain name server and retrieves the corresponding IP address for the web server.
- The web browser connects to the web server and sends an HTTP request (via the protocol stack) for the desired web page.
- The web server receives the request and checks for the desired page. If the page exists, the web server sends it. If the server cannot find the requested page, it will send an HTTP 404 error message. (404 means 'Page Not Found' as anyone who has surfed the web probably knows.)
- The web browser receives the page back and the connection is closed.
- The browser then parses through the page and looks for other page elements it needs to complete the web page. These usually include images, applets, etc.
- For each element needed, the browser makes additional connections and HTTP requests to the server for each element.
- When the browser has finished loading all images, applets, etc. the page will be completely loaded in the browser window.
Most Internet protocols are specified by Internet documents known as a Request For Comments or RFCs. RFCs may be found at several locations on the Internet.
WWW is an Internet navigation tool that helps you to find and retrieve information links to other WWW pages. The WWW is a distributed hypermedia environment consisting of documents from around the world. The documents are linked using a system known as hypertext, where elements of one document may be linked to specific elements of another document. The documents may be located on any computer connected to the Internet. The word “document” is not limited to text but may include video, graphics, databases and a host of other tools.
The World Wide Web is described as a “wide area hypermedia information initiative among to give universal access to large universe of documents”. World Wide Web provides users on computer networks with a consistent means to access a variety of media in a simplified fashion. A popular software program to search the Web is called Mosaic, the Web project has modified the way people view and create information. It has created the first global hypermedia network.
Once again the WWW provides an integrated view of the Internet using clients and servers. As discussed earlier, clients are programs that help you seek out information while servers are the programs that find information to the clients. WWW servers are placed all around the Internet.
The operations of the Web mainly rely on hypertext as its means of interacting with users. But what is hypertext? Hypertext as such is the same as regular text that is it can be written, read, searched or edited; however, hypertext contains connections within the text to other documents. The hypertext links are called hyperlinks. These hyperlinks can create a complex virtual web of connections.
Hypermedia is an advanced version of hypertext documents as it contains links not only to other pieces of text but also to other forms of media such as sounds, images and movies. Hypermedia combines hypertext and multimedia.
Usenet and Newsgroups
In Internet there exists another way to meet people and share information. One such way is through Usenet newsgroups. These are special groups set up by people who want to share common interests ranging from current topics to cultural heritages. These are currently thousands of Usenet newsgroups.
The Usenet can be considered as another global network of computers and people, which is interwined with the Internet. However, Usenet does not operate interactively like the Internet, instead Usenet machines store the messages sent by users. Unlike mail from mailing lists, the news articles do not automatically fill your electronic mailbox. For accessing the information on newsnet, one needs a special type of program called a newsreader. This program help in retrieving only the news you want from Usenet storage site and display it on your terminal. Usenet is like living thing, New newsgroups gets added, the groups which have too much traffic get broken up into smaller specialized groups, the groups even can dissolve themselves. However, all of this occurs based on some commonly accepted rules and by voting. For Usenet, there is no enforcement body; it entirely depends on the cooperation of its computers owners and users.
The newsgroups are really meant fro interaction of people who share your interests. You can post your own questions as well as your answers to the questions of others, on the Usenet. One thing, which is worth mentioning here, is that when one is interacting wit people on Internet certain mannerism should be adopted. These rules are sometimes called “netiquette”. In a face-to-face conversation you can always see a person’s facial gestures and hand movements and can ascertain whether he is teasing or is being sarcastic or sometimes even lying. However, in on-line interaction one cannot see the person one is interacting with. The rules of netiquette may help to compensate some of these limitations of this on-line environment.
File Transfer Protocol (FTP)
FTP (File Transfer Protocol), a standard Internet protocol, is the simplest way to exchange files between computers on the Internet. Like the Hypertext Transfer Protocol (Hypertext Transfer Protocol), which transfers displayable Web pages and related files, FTP is an application protocol that uses the Internet's TCP/IP protocols. FTP is commonly used to transfer Web page files from their creator to the computer that acts as their server for everyone on the Internet. It's also commonly used to downloading programs and other files to the computer from other servers. However, for such transfer you need an account name on a host and the password. The FTP program will make connection with the remote host, which will help you to browse its directories and mark files for transfer. However, you cannot look at the contents of a file while you are connected via FTP. You have to transfer the copy and then look at it once it is on your own account.
FTP includes many commands but only few are used to retrieve a file. A user needs to understand the three basic commands to connect to remote computer, retrieve a copy of file and exit the FTP program. The commands with their meanings are:
| Command | Purpose |
|---|---|
| Open | connect to a remote computer |
| get | retrieve a file from the computer |
| bye | terminate the connection and leave the FTP program |
Transferring a file via FTP requires two participants: an FTP client program and FTP server program. The FTP client is the program that we run on our computers. The FTP server is the program that runs on the huge mainframe somewhere and stores tens thousands of files. It is similar to an online library of files. The FTP client can download (receive) or upload (send) files to the FTP server. Using Web browser you can download the files but you can not upload the files. FTP applications will help you to upload the files to the web sites, which you are maintaining.
FTP only understands two basic file formats. It classifies each file either as a text file or a binary file. A text file contains a sequence of characters collected into lines. Although computers used ASCII encoding for text files, FTP includes commands to translate between ASCII and other character encoding. FTP uses the classification binary file for all nontext files. The user must specify binary for any file that contains:
FTP only understands two basic file formats. It classifies each file either as a text file or a binary file. A text file contains a sequence of characters collected into lines. Although computers used ASCII encoding for text files, FTP includes commands to translate between ASCII and other character encoding. FTP uses the classification binary file for all nontext files. The user must specify binary for any file that contains:
- A computer program
- Audio data
- A graphic or video image
- A spreadsheet
- A document from a word processor
- A compressed file
FTP service compress files to reduce the total amount of disk space the files require. Before transferring a file user must tell FTP that the file contains ASCII text or nontext file. FTP assumes to perform ASCII transfers unless the user enters the binary command.
There are many FTP programs that you can download from the Internet. Windows has its own command line based FTP program. To execute it, select Run from Windows taskbar and type FTP and press enter. By typing open command you can connect to any ftp server. To connect to FTP server you must have a login name and the password. Most of the FTP servers allow anonymous connections. In this case username is anonymous and password is your e-mail address.
Another important FTP program, which is available as a shareware, is WSFTP. Using this window based program it is easier to maintain your web site.
Telnet
The working of TELNET,
- The commands and characters are sent to the operating system on the common server computer.
- The local operating system sends these commands and characters to a TELNET client program, which is located on the same local computer.
- The TELNET client transforms the characters entered by the user to an agreed format known as Network Virtual Terminal (NVT) characters and sends them to the TCP/IP protocol stack of the server computer. NVT is the common device between the client and server.
- The commands and text are first broken into TCP and then IP packets and are sent across the physical medium from the local client computer to the server.
- At the server computer’s end, the TCP/IP software collects all the IP packets, verifies their correctness and reconstructs the original command and handover the commands or text to that computer operating system.
- The operating system of the server computer hands over these commands or text to the TELNET server program, which is executing on that remote computer.
- The TELNET server program on the remote server computer then transforms the commands or text from the NVT format to the format understood by the remote computer.
- The TELNET cannot directly handover the commands or text to the operating system so TELNET hands over the commands/text to the Psuedo-terminal driver.
The Pseudo-terminal driver program then hands over the commands or text to the operating system of the remote computer, which then invokes the application program on the remote server.
There are many databases available on the Internet. You can explore these databases using Telnet. There are going to be many Internet services yet to be created. Every year and better means of accessing the treasures of the Internet is appearing in which Telnet is the key for accessing.
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