~ Web Technologies


Client and server side processing

Server-side scripting is a technique used in web development which involves employing scripts on a web server which produce a response customized for each user's (client's) request to the website. The alternative is for the web server itself to deliver a static web page. Scripts can be written in any of a number of server-side scripting languages that are available (see below). Server-side scripting is distinguished from client-side scripting where embedded scripts, such as JavaScript, are run client-side in a web browser, but both techniques are often used together.

Server-side scripting is often used to provide a customized interface for the user. These scripts may assemble client characteristics for use in customizing the response based on those characteristics, the user's requirements, access rights, etc. Server-side scripting also enables the website owner to hide the source code that generates the interface, whereas with client-side scripting, the user has access to all the code received by the client. A down-side to the use of server-side scripting is that the client needs to make further requests over the network to the server in order to show new information to the user via the web browser. These requests can slow down the experience for the user, place more load on the server, and prevent use of the application when the user is disconnected from the server.

When the server serves data in a commonly used manner, for example according to the HTTP or FTP protocols, users may have their choice of a number of client programs (most modern web browsers can request and receive data using both of those protocols). In the case of more specialized applications, programmers may write their own server, client, and communications protocol, that can only be used with one another.

Programs that run on a user's local computer without ever sending or receiving data over a network are not considered clients, and so the operations of such programs would not be considered client-side operations.

Netscape introduced an implementation of JavaScript for server-side scripting with Netscape Enterprise Server, first released in December, 1994 (soon after releasing JavaScript for browsers).

Server-side scripting was later used in early 1995 by Fred DuFresne while developing the first web site for Boston, MA television station WCVB. The technology is described in US patent 5835712. The patent was issued in 1998 and is now owned by Open Invention Network (OIN). In 2010 OIN named Fred DuFresne a "Distinguished Inventor" for his work on server-side scripting.

Today, a variety of services use server-side scripting to deliver results back to a client as a paid or free service. An example would be WolframAlpha, which is a computational knowledge engine that computes results outside the clients environment and returns the computed result back. A more commonly used service is Google's proprietary search engine, which searches millions of cached results related to the user specified keyword and returns an ordered list of links back to the client. Apple's Siri application also employs server-side scripting outside of a web application. The application takes an input, computes a result, and returns the result back to the client.

Client Side Processing - Client side info

Typically, a client is a computer application, such as a web browser, that runs on a user's local computersmartphone, or other device, and connects to a server as necessary. Operations may be performed client-side because they require access to information or functionality that is available on the client but not on the server, because the user needs to observe the operations or provide input, or because the server lacks the processing power to perform the operations in a timely manner for all of the clients it serves. Additionally, if operations can be performed by the client, without sending data over the network, they may take less time, use less bandwidth, and incur a lesser security risk.

When the server serves data in a commonly used manner, for example according to standard protocols such as HTTP or FTP, users may have their choice of a number of client programs (e.g. most modern web browsers can request and receive data using both HTTP and FTP). In the case of more specialized applications, programmers may write their own server, client, and communications protocol which can only be used with one another.

Programs that run on a user's local computer without ever sending or receiving data over a network are not considered clients, and so the operations of such programs would not be termed client-side operations.

In a computer security context, client-side vulnerabilities or attacks refer to those that occur on the client / user's computer system, rather than on the server side, or in between the two. As an example, if a server contained an encrypted file or message which could only be decrypted using a key housed on the user's computer system, a client-side attack would normally be an attacker's only opportunity to gain access to the decrypted contents. For instance, the attacker might cause malware to be installed on the client system which allowed the attacker to view the user's screen, record the user's keystrokes, steal copies of the user's encryption keys, etc. Alternatively, an attacker might employ cross-site scripting vulnerabilities in order to execute malicious code on the client's system without needing to install any permanently resident malware

 

Distributed computing projects such as SETI@home and the Great Internet Mersenne Prime Search, as well as Internet-dependent applications like Google Earth, rely primarily on client-side operations. They initiate a connection with the server (either in response to a user query, as with Google Earth, or in an automated fashion, as with SETI@home), and request some data. The server selects a data set (a server-side operation) and sends it back to the client. The client then analyzes the data (a client-side operation), and, when the analysis is complete, displays it to the user (as with Google Earth) and/or transmits the results of calculations back to the server (as with SETI@home).

In the context of the World Wide Web, commonly encountered computer languages which are evaluated or run on the client side include:


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