Web Standards

HTTP Protocol

The web is run on port 80. You are probably wondering what "port 80" is, right (whether you actually are or not is irrelevant)? Well, the answer is easy (not really). See, the Internet and the web are different. The Internet is the infrastructure (ie the physical wires, the server hardware, etc) and the web is the ideas and the software. I say ideas because before the web the Internet was a mess of wires and powerful computers using POP3 and SMTP for communication, FTP for file transfer, and TELNET for remote shell access, among others. Then the web came along, and Internet use spread to the home and all across the world. See, in plain terms, a web server broadcasts HTML to all connected clients on port 80, so port 80 is the "HTTP port." HTTP is the protocol, or set of standards for port 80 and its software. The client software is your browser, (ie probably Internet Explorer but hopefully Firefox), and the server is something like Apache or IIS(uug). This relates to hacking, as you will see later, but first you need to know more about HTTP. (the spaces before the < & > are put in so this isnt thought of as HTML)

< html >

< body >

< img src="image.png" >< br >

< div align="center" >text< /div >

< /body >

< /html >

If Apache is serving that, and Firefox picks it up, It will replace the < img src... etc with the image found at image.png relative to the working directory of the page requested, (ie ./, current dir), and the < div... is turned into text printed in the middle of the page. Since the code is processed from top to bottom, the br means that the browser should skip down one line and start the rest from there. The top two and bottom two lines tell the browser what part of the page it is reading. You migh have noticed the < /div >, the < /body >, etc. They "close" the tag. Tag is a term for anything in s, and they must be opened (ie introduced) and closed (ie < /tag >). If you want to learn HTML tagging, just head over to our close friend Google and do a search.

Since you haven't gotten to the programming section, and currently I have not even wrote it, I will show you a web server example in the simplest form I can think of that will work on any OS you are currently using. So the obvious choice is JAVA:

import java.net.*; import java.io.*; import java.util.*;

public class jhttp extends Thread {

Socket theConnection;

static File docroot;

static String indexfile = "index.html";

public jhttp(Socket s) {

theConnection = s;

}

public static void main(String[] args) {

int thePort;

ServerSocket ss;

// get the Document root

try {

docroot = new File(args[0]);

}

catch (Exception e) {

docroot = new File(".");

}

// set the port to listen on

try {

thePort = Integer.parseInt(args[1]);

if (thePort < 0 || thePort > 65535) thePort = 80;

}

catch (Exception e) {

thePort = 80;

}

try {

ss = new ServerSocket(thePort);

System.out.println("Accepting connections on port "

+ ss.getLocalPort());

System.out.println("Document Root:" + docroot);

while (true) {

jhttp j = new jhttp(ss.accept());

j.start();

}

}

catch (IOException e) {

System.err.println("Server aborted prematurely");

}

}

public void run() {

String method;

String ct;

String version = "";

File theFile;

try {

PrintStream os = new PrintStream(theConnection.getOutputStream());

DataInputStream is = new DataInputStream(theConnection.getInputStream());

String get = is.readLine();

StringTokenizer st = new StringTokenizer(get);

method = st.nextToken();

if (method.equals("GET")) {

String file = st.nextToken();

if (file.endsWith("/")) file += indexfile;

ct = guessContentTypeFromName(file);

if (st.hasMoreTokens()) {

version = st.nextToken();

}

// loop through the rest of the input li

// nes

while ((get = is.readLine()) != null) {

if (get.trim().equals("")) break;

}

try {

theFile = new File(docroot, file.substring(1,file.length()));

FileInputStream fis = new FileInputStream(theFile);

byte[] theData = new byte[(int) theFile.length()];

// need to check the number of bytes rea

// d here

fis.read(theData);

fis.close();

if (version.startsWith("HTTP/")) { // send a MIME header

os.print("HTTP/1.0 200 OKrn");

Date now = new Date();

os.print("Date: " + now + "rn");

os.print("Server: jhttp 1.0rn");

os.print("Content-length: " + theData.length + "rn");

os.print("Content-type: " + ct + "rnrn");

} // end try

// send the file

os.write(theData);

os.close();

} // end try

catch (IOException e) { // can't find the file

if (version.startsWith("HTTP/")) { // send a MIME header

os.print("HTTP/1.0 404 File Not Foundrn");

Date now = new Date();

os.print("Date: " + now + "rn");

os.print("Server: jhttp 1.0rn");

os.print("Content-type: text/html" + "rnrn");

}

os.println("< HTML >< HEAD >< TITLE >File Not Found< /TITLE >< /HEAD >");

os.println("< BODY >< H1 >HTTP Error 404: File Not Found< /H1 >< /BODY >< /HTML >");

os.close();

}

}

else { // method does not equal "GET" if (version.startsWith("HTTP/")) { // send a MIME header os.print("HTTP/1.0 501 Not Implementedrn"); Date now = new Date(); os.print("Date: " + now + "rn"); os.print("Server: jhttp 1.0rn"); os.print("Content-type: text/html" + "rnrn"); }

os.println("< HTML >< HEAD >< TITLE >Not Implemented< /TITLE >"); os.println("< BODY >< H1 >HTTP Error 501: Not Implemented< /H1 >< /BODY >< /HTML >"); os.close(); }

}

catch (IOException e) {

}

try { theConnection.close(); }

catch (IOException e) { }

}

public String guessContentTypeFromName(String name) { if (name.endsWith(".html") || name.endsWith(".htm")) return "text/html"; else if (name.endsWith(".txt") || name.endsWith(".java")) return "text/plain"; else if (name.endsWith(".gif") ) return "image/gif"; else if (name.endsWith(".class") ) return "application/octet-stream"; else if (name.endsWith(".jpg") || name.endsWith(".jpeg")) return "image/jpeg"; else return "text/plain"; }

}

I learned the basics of JAVA web server programming from "JAVA Network Programming" by Elliotte Rusty Harold. Now you don't need to know JAVA to be able to understand that, even though it might not seem like that at first. The important thing to look for when examining the code it the os.print("") commands. There is nothing fancy being used to get the data to the browser, you don't have to mutate the data, its sending plain HTML via a simple command. The plain and simple truth is that the browser is doing the majority of the difficult stuff, when speaking about this simple server. But in complicated servers there is server-side scripting, etc. Webs are much more complicated than just a simple server and Internet Explorer, such as Flash and JAVA Applets (run on clients machine in browser) and server-side stuff like PHP and PEARL (displayed on clients browser as plain HTML but executed as scripting on the server). T

he code above is a good way to learn the HTTP standards, even though the program itself ignores most of the regulations. The web browser not only understands HTML but also knows that incoming connection starting with 404 means that the page is missing, etc. It also knows that when "image/gif" is returned the file is an image of type gif. These are not terms the stupid server made up. They are web standards. Generally speaking, there are two standards. There is the w3 standard (ie the real standard based on the first web servers and browsers) and the Microsoft standard (ie the Internet Explorer, IIS and NT standards). The standards are there so anyone can make a server or client and have it be compatible with (nearly) everything else.

Hiding your Connection

If you have a copy of Visual Basic 6, making a web browser is easy, thanks to Winsock and the code templates included, so I will not put in an example of that. Instead I will explain cool and potentially dangerous things you can do to keep yourself safe. I know those words put together doesn't make sense (ie potentially dangerous and safe), but you will see in a moment. I'm talking about PROXIES. (anonymous proxy servers, to be exact). You connect to the internet on port 80 through the proxy server, thus hiding your real IP. There are many obvious applications for this, but it is also the only really potentially dangerous thing so far, so I will restate what I have written at the top: Whatever you do with this info is your responsibility. I provide information and nothing more. With that said, there is nothing illegal about using an anonymous proxy server as long as it is free and you are harming no one by using it. But if you think you are completely safe using one, you are deadly wrong. They can simply ask the owners of the proxy what your IP is if they really want to find you. If you join a high anonymous server, the chance of them releasing your IP is pretty low for something like stealing music, but if you do something that would actually warrant jail time, they probably will be able to find you. www.publicproxyservers.com is a good site for finding these servers.

The last trick related to web servers and port 80 is a simple one. First, find a free website host that supports PHP and use the following code:

If the address of this file is http://file.com/script.php, to download the latest Fedora DVD you would go to the following address: http://file.com/script.php?destfile=linuxiso.org/download.php/611/FC3-i386-DVD.iso &password=passwd

You can change "passwd" to whatever password you want. This will make any onlookers think you are connected to http://file.com. You are still limited to the speed of your connection, but you are using the bandwidth of the web host

Whatever you do with the above information is solely your responsibility.

Mike Vollmer --- eblivion
http://eblivion.sitesled.com

Troubleshooting Computer Freeze (Lockup) Problems

How familiar does the following sound? Your computer was working... Read More

Computer Performance Tips

Introduction In this article I will clearly spell out the... Read More

2 PC Annoyances and How To Solve Them!

I have a love-hate relationship with my computer.In fact, often... Read More

Help, I Need a New HDTV! (Part 5 of 5)

Feeling overwhelmed in selecting a new TV? With all the... Read More

15 Good Programming Habits

1. Before sitting down for coding, you must have formal... Read More

D2X Digital SLRCoolpix 8800 Actually Refers to Two Nikon Cameras

Addressing a D2X Digital SLRCoolpix 8800 search, this article provides... Read More

Cache In Your Chips And Get A Bus!

Computer related terminology could sometimes be daunting to newcomers. These... Read More

Your Affiliate Business - Peripherals, Software, Computers

I have always been interested in computers, but in the... Read More

Windows PDA Medical Software Benefits

PDA Medical BenefitsIf you are concerned about your medical history,... Read More

Windows Task Manager in English

You use Ctrl+Alt+Del to see what's running on your PC,... Read More

10 Tips to Stay Safe and Secure Online

The Internet can be a dangerous place.While you're enjoying the... Read More

Basic Computer Maintenance

One of the most common questions computer users ask is,... Read More

The Help Desk

When you think of a help desk, what do you... Read More

SmartCar Memory Stick for LapTop Transfer Data

With the new technology used to transfer information to from... Read More

Lightning Season: How to Avoid Data Loss

We have just entered the time of year that most... Read More

Home Video? Bring it On

So you got yourself a digital camcorder. If you want... Read More

What are the Main Components of Any Computer, and Which are the Most Critical to Its Performance?

Computers are everywhere, and vary in specification, brands, sizes, shaped,... Read More

A Beginners Guide to Avoiding Viruses

"Aaaaaahhhhhh! I've been invaded by a virus!" Getting a virus... Read More

Ergonomics and Healthy Computing - Positioning Your Body For Maximum Comfort At Your Computer

Do you remember the old saw about how computers would... Read More

Taking Advantage of the iPod Experience

Music lovers have been carrying around radios and other bulky... Read More

Setting File Permissions On A Unix Server

File permissions are one of the strengths that the Unix... Read More

How to Protect your PC from Spyware in the Cyber Age

Wouldn't you be shocked to find that your personal sensitive... Read More

How Does a Palm Pilot Work?

Just The Facts, Ma'mPalm pilots are all the rage now.... Read More

7 Reasons NOT to Take Your Laptop on Holiday!

Heading off on vacation soon?Then perhaps you're tempted to take... Read More

Why Build Your Own Gaming Computer?

The best way to get the gaming computer that you... Read More