S-Vizion

Understanding Client Side and Server Side Processes For Websites

February 27th, 2011 | by | web development

Feb
27

Bandwidth Diagram

For a Developer, or a Someone Running a in General it is Important to understand the difference between Client side processes and Server Side processes. I have been getting alot of questions asked about things from both Developers and Clients who do not understand the difference so I figured I would write a short article explaining the difference.

Web pages are displayed in your browser on your local machine. Just like a customer or client for a restaurant, you and your browser are a client using a Web site. The Web site is displayed by your browser, which interprets code that was sent to it. In general this code will be primarily HTML, but may also contain anything supported by your browser such as javascript, flash movies, and more.

The machine where the Web site actually resides is called a Web server. When you send a request for a Web page by entering a Web site address, this request is sent to a Web Server. The Web server then sends the Web page to your browser. The interesting thing about a Web server is that it can manipulate the code within a Web page before sending it to your browser. For most Web pages, no manipulation is done. Rather, the server simply sends a copy to the browser and the browser does the work of displaying the code.

A Web Server can manipulate what is included in a Web page before sending it. When the request is made to a server to send a Web page, the server can actually execute a program instead. This can be a program written in a variety of languages. Some of the programming languages and technologies that can be used are Active Server Pages (ASP), PHP, C/C++, and Ruby, Java Server Pages (JSP), and more. Of course, in order to use any of these languages, the server must support them.

An important issue when working with Web applications is to remember that the Web server is separate from the Web browsers that will use a Web site’s pages. The Web server can be located anywhere in the world — or even off the world! The browser is generally on a machine you are using. Stated a different way, you can act as a customer, or client, using a browser to access a Web site that is located on a Web server.

The programs running on the Web Server are server side programs because they are on the side of the internet that the Web server is on. The browser being used to access the Web site is on the same side of the Web as you, the client side. If code is executed on the Web server, it is considered server side code. If code is executed on your browser, it is considered client-side. Because the internet is vast, the client side and server side programs are not constantly in contact with each other. Because of this, there is code that you can use on the server and there is code that you can use on the client.

What do you do on the server?

There are a number of types of programming things that can be done on the server. One of the primary functions you can do with code is to prepare the code that is to be sent to the Web browser. This includes such tasks as building pages customized for the type of browser that requested a page. It could also include doing tapping into a database to create information for a Web page. A very popular server side program is a Visitor Counter that keeps track of the number of people who have accessed a Web Site. The counter program would keep track of people who have come and store the information. It would also provide the actual number for any Web pages that are sent back to a browser.

What do you do on the client?

HTML, javascript, Flash files, ActiveX controls, Java applets, and a number of other technologies can be executed on the client side. You can execute any technology supported by your browser. Client side programming is used because the browser is separate from the server. By including code within a web page, a number of features can be added to a Web page without the need to send information to the Web Server which takes time. Tasks done on the client side include data validation, special formatting features that go beyond HTML, controls that take care of page navigation and ad presentation, and more.

Email Clients

This is the important part now that you have a basic understanding of the fundamentals of how the Web Works, let’s talk about what exactly a Client side Application is.

First a Client side application is a Program Written in a language and compiled to work on your Operating System, for example Outlook, Internet Explorer, Firefox, Thunderbird, etc, etc.

A client side application can not change what a server side process does it can only interact with it in certain ways. Lets take a email client to start since that’s were I hear the confusion constantly coming from.

Your email is stored on your Server just like if you connected your Digital camera to your Home PC and stored your pictures there. Now The Server is hosted somewhere and it is built very much like a normal pc. It has all the same things a normal pc would have except to save ram and disk space they don’t have window managers since they aren’t very useful. Anyway back to the email. Your email accounts, messages, passwords, etc are stored on the Server. You would then retrieve these emails using a client such as Outlook, Evolution, Thunderbird, KMail, etc. You set these clients up with your Mail Port ( mail.yourserver.com ) and you add you Account name and password. It then retrieves the email and stores it on your desktop, phone, or wherever you store it.

Now the catch is you have to have the correct Settings to Access this information or it wouldn’t be secure. Now if you forget the password to your email account, or your change it, or your computer loses it because of a hard shut-down, then you will have to change this password on the Server Side through your control panel or through your web mail account. Once changed you have to change it in your Client Side application to connect.

Hopefully this helps you get a better understanding of how the internet works.

Tags: , , ,

No Comments »

BandWidth Explained

January 28th, 2011 | by | web development

Jan
28

Bandwidth Diagram

Most companies offer a variety of bandwidth options in their plans. So exactly what is bandwidth as it relates to hosting? Put simply, bandwidth is the amount of traffic that is allowed to occur between your site and the rest of the internet. The amount of bandwidth a hosting company can provide is determined by their network connections, both internal to their data center and external to the public internet.

Network Connectivity

The internet, in the most simple of terms, is a group of millions of computers connected by networks. These connections within the internet can be large or small depending upon the cabling and equipment that is used at a particular internet location. It is the size of each network connection that determines how much bandwidth is available. For example, if you use a DSL connection to connect to the internet, you have 1.54 Mega bits (Mb) of bandwidth. Bandwidth therefore is measured in bits (a single 0 or 1). Bits are grouped in bytes which form words, text, and other information that is transferred between your computer and the internet.

If you have a DSL connection to the internet, you have dedicated bandwidth between your computer and your internet . But your internet may have thousands of DSL connections to their location. All of these connections aggregate at your internet , who then has their own dedicated connection to the internet (or multiple connections) which is much larger than your single connection. They must have enough bandwidth to serve your needs as well as all of their other customers. So while you have a 1.54Mb connection to your internet , your internet may have a 255Mb connection to the internet so it can accommodate your needs and up to 166 other users (255/1.54).

Traffic

A very simple analogy to use to understand bandwidth and traffic is to think of highways and cars. Bandwidth is the number of lanes on the highway and traffic is the number of cars on the highway. If you are the only car on a highway, you can travel very quickly. If you are stuck in the middle of rush hour, you may travel very slowly since all of the lanes are being used.

Traffic is simply the number of bits that are transferred on network connections. It is easiest to understand traffic using examples. One Gigabyte is 2 to the 30th power (1,073,741,824) bytes. One gigabyte is equal to 1,024 megabytes. To put this in perspective, it takes one byte to store one character. Imagine 100 file cabinets in a building, each of these cabinets holds 1000 folders. Each folder has 100 papers. Each paper contains 100 characters – A GB is all the characters in the building. An MP3 song is about 4MB, the same song in wav format is about 40MB, a full length movie can be 800MB to 1000MB (1000MB = 1GB).

If you were to transfer this MP3 song from a web site to your computer, you would create 4MB of traffic between the web site you are downloading from and your computer. Depending upon the network connection between the web site and the internet, the transfer may occur very quickly, or it could take time if other people are also downloading files at the same time. If, for example, the web site you from has a 10MB connection to the internet, and you are the only person accessing that web site to your MP3, your 4MB file will be the only traffic on that web site. However, if three people are all downloading that same MP3 at the same time, 12MB (3 x 4MB) of traffic has been created. Because in this example, the host only has 10MB of bandwidth, someone will have to wait. The network equipment at the hosting company will cycle through each person downloading the file and transfer a small portion at a time so each person’s file transfer can take place, but the transfer for everyone downloading the file will be slower. If 100 people all came to the site and downloaded the MP3 at the same time, the transfers would be extremely slow. If the host wanted to decrease the time it took to files simultaneously, it could increase the bandwidth of their internet connection (at a cost, due to upgrading equipment).

Hosting Bandwidth

In the example above, we discussed traffic in terms of downloading an MP3 file. However, each time you visit a web site, you are creating traffic, because in order to view that web page on your computer, the web page is first downloaded to your computer (between the web site and you) which is then displayed using your browser software (Internet Explorer, Netscape, etc.) . The page itself is simply a file that creates traffic just like the MP3 file in the example above (however, a web page is usually much smaller than a music file).

A web page may be very small or large depending upon the amount of text and the number and quality of images integrated within the web page. For example, the home page for CNN.com is about 200KB (200 Kilobytes = 200,000 bytes = 1,600,000 bits). This is typically large for a web page. In comparison, Yahoo’s home page is about 70KB.

How Much Bandwidth Is Enough?

It depends (don’t you hate that answer). But in truth, it does. Since bandwidth is a significant determinant of hosting plan prices, you should take time to determine just how much is right for you. Almost all hosting plans have bandwidth requirements measured in months, so you need to estimate the amount of bandwidth that will be required by your site on a monthly basis

If you do not intend to provide file download capability from your site, the formula for calculating bandwidth is fairly straightforward:

Average Daily Visitors x Average Page Views x Average Page Size x 31 x Fudge Factor

If you intend to allow people to download files from your site, your bandwidth calculation should be:

[(Average Daily Visitors x Average Page Views x Average Page Size) +
(Average Daily File Downloads x Average File Size)] x 31 x Fudge Factor

Let us examine each item in the formula:

Average Daily Visitors – The number of people you expect to visit your site, on average, each day. Depending upon how you market your site, this number could be from 1 to 1,000,000.

Average Page Views – On average, the number of web pages you expect a person to view. If you have 50 web pages in your web site, an average person may only view 5 of those pages each time they visit.

Average Page Size – The average size of your web pages, in Kilobytes (KB). If you have already designed your site, you can calculate this directly.

Average Daily File Downloads – The number of downloads you expect to occur on your site. This is a function of the numbers of visitors and how many times a visitor downloads a file, on average, each day.

Average File Size – Average file size of files that are downloadable from your site. Similar to your web pages, if you already know which files can be downloaded, you can calculate this directly.

Fudge Factor – A number greater than 1. Using 1.5 would be safe, which assumes that your estimate is off by 50%. However, if you were very unsure, you could use 2 or 3 to ensure that your bandwidth requirements are more than met.

Usually, hosting plans offer bandwidth in terms of Gigabytes (GB) per month. This is why our formula takes daily averages and multiplies them by 31.

Summary

Most personal or small business sites will not need more than 1GB of bandwidth per month. If you have a web site that is composed of static web pages and you expect little traffic to your site on a daily basis, go with a low bandwidth plan. If you go over the amount of bandwidth allocated in your plan, your hosting company could charge you over-usage fees, so if you think the traffic to your site will be significant, you may want to go through the calculations above to estimate the amount of bandwidth required in a hosting plan.

Tags: , , , , , , , ,

1 Comment »