Client Server Architecture of Internet.

Client Server Architecture of Internet.

The concept of client-server architecture is important in the context of Internet because Internet works based on it. It is an application that is composed of a server program and a client program. These two programs

communicate through networks. The server program is often called server, a server is a piece of software, not some hardware. The computer on which the server program is executed is called a server computer.

The client program is also called client. 

The server program has the following characteristics:

1. It is a program designed for providing a particular service.
2. When the server computer boots up, the server program is usually invoked automatically, the service is always available.
3. It waits passively for clients requests Upon receiving one request, it performs the necessary computation and returns the result to the client.
4. In many applications, a server is designed such that it can serve multiple clients simultaneously.

The client program has the following characteristics:

1. It is an application program executed by an end user on a local computer.

1. When it needs a service, it sends a request to the server programs, and then waits for the response from the server program.

1. It can request multiple services when it is necessary.

Internet Protocol:

The Internet Protocol is the method use a transport protocol to send and receive data from one computer to another. It is the set of communications protocols that implement the protocol stack on which the Internet runs.

A protocol stack is a complete set of protocol layers that work together to provide networking capabilities.It most commonly refers a  set of rules that enables computers to connect and transmit data to one another; this is also called a communications protocol. The Internet protocol suite is sometimes called the TCP/IP protocol suite, which refers to the two most important protocols in it: the transmission control protocol(TCP) and Internet Protocol(IP).

Some important Protocol are:

Simple Mail Transfer Protocol:

It is the protocol used for electronic mail (E-mail) transmission across the internet Protocol(IP) networks. SMTP uses TCP port 25. SMTP is used by most of the email systems to send messages from one server to another over the Internet. In simple words we cans say that SMTP is mainly used to send messages or mails from a mail client to a mail server SMTP  actually performs two transfers:

1. from the senders computer to the sender's SMTP server and

1. from the sender's SMTP server to the receiver's SMTP server.

POP3: 

The Post Office Protocol (POP) is an application-layer Internet standard protocol used by local e-mail clients to retrieve e-mail from a remote server over a TCP/IP connection. The "3" means it is the third revision of the standard; POP1 and POP2 were made obsolete by POP3. A POP3 mail server receives e-mails and filters them into the appropriate user folders. When a user connects to the mail server to retrieve his mail, the messages are downloaded from mail  server to the user's hard disk.