Protocols are the rules that describe how clients and servers communicate across a network. There are several different protocols used by the Internet.
The Internet uses several different protocols to communicate across the network. The protocols used currently were developed many years ago, and are similar in concept to the rules of diplomatic interaction that dictate who speaks first, who bows to whom and so forth.
Hypertext Transfer Protocol (HTTP)
HTTP is a protocol used to transfer Web pages from a Web server to a Web client. The Web client is
usually a Web browser. Specifically, HTTP is the set of rules required to exchange files, such as text,
images, video and multimedia content, across the Web.
An essential concept of HTTP is that files contain references to other files, so they are “linked” to one another. The files transferred by HTTP are HTML files and others that HTTP can serve. Web servers are often called HTTP servers.
Port no: 80
File Transfer Protocol (FTP)
FTP was originally developed to allow researchers to give one another access to programs and large data files. The early users protected most of their file access with simple user IDs and passwords, but many set aside small parts of FTP sites for anonymous, or general, access.
To obtain access to files
through an anonymous FTP server, you use the general user ID “anonymous” and provide your e-mail address as the password. Anonymous FTP site access is so popular that many FTP clients connect you automatically. FTP servers are scattered throughout the Internet, and are generally accessible to anyone.
Businesses have discovered many uses for FTP servers as efficient information, access and distribution points.
For instance, when you download software programs and documents from Web sites, you are usually transferred to FTP sites for the actual download. This process takes place transparently (e.g., the user is unaware of which protocol is downloading the program).
FTP is also used to publish Web pages to a Web server. You simply upload your Web page files to an FTP server.
After the upload is complete, Web browsers using HTTP can access your Web pages.
Port No: 21
Electronic Mail (E-Mail)
E-mail involves two mail servers: an outgoing and an incoming. You send e-mail to others with an
outgoing mail server using the Simple Mail Transfer Protocol (SMTP).
You receive e-mail from an
incoming mail server using the Post Office Protocol (POP) or the Internet Message Access Protocol
Port No: SMTP: 25, POP3: 110, IMAP: 143