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

In The News:

How to Reduce Credit Card Fraud  The New York Times
Why is 5G important? | About Verizon  Verizon Communications

Cache In Your Chips And Get A Bus!

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

Flow Text Around a Graphic in Microsoft Word

Flow Text Around a GraphicQuestion: I have inserted a photo... Read More

Gain Control Over Your Screensavers With These Simple Steps

We all enjoy our favorite screensavers but in the same... Read More

Cisco CCNA Certification: Five Things To Do DURING The Exam

There are plenty of articles out there about how to... Read More

Can Movie Theatres Compete with Home HD TV in the Future?

The battle is heating up for market share, home movie... Read More

Digital Cameras: How Many Pixels Do I Need?

With the bewildering number of digital cameras on the market,... Read More

Faster Browsing Tips

IF WE say that it was mainly because of the... Read More

How Do MP3 Players Work? Digital Audio Technology Revolutionizes Music Enjoyment

Millions have enjoyed recorded music since 1877 when Thomas Edison... Read More

Learning To Navigate Ciscos Online Documentation

When studying for your Cisco CCNA, CCNP, or CCIE exam,... Read More

Compile .BAT Files into Native Windows Applications (.EXE)

Since the DOS days, batch files have been one of... Read More

Upgrading Your PC for Non-experts

IntroOne of the big advantages of PCs over earlier types... Read More

New Computer? Steps to Protect Your Computer Before Connecting to the Internet

Getting a new computer should be an exciting and gratifying... Read More

HTML Explained: Part 1

Want to save money while promoting your web-based business? Of... Read More

Email Management

If you utilize a computer at home or work it... Read More

Why Get a Microsoft MCSE Certification?

In the years of the dot com boom and bust,... Read More

Best PC Pocket GPS

Stop Getting LostOne of the greatest uses for a pocket... Read More

Is Desktop Search Deserving?

Google, in their march to stay ahead of the pack... 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

Buying A PC Flat Screen Monitor

For six years, my Samsung PC 13.8 inch SyncMaster conventional... Read More

Help, I Need a New HDTV! (Part 1 of 5)

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

What Are You Looking For In A Cheap MP3 Player?

Are you stymied by the vast offerings in cheap mp3... Read More

Cisco Certification: Building Your Own Home Lab, Part I

CCNAs and CCNA candidates hear it all the time: â??Get... Read More

Things You Can Do To Speed Up Your Computer

Upgrading your processor will always speed up your computer, but... Read More

Printing Multiple Copies of Photos

I do a holiday letter every year and send them... Read More

Setting File Permissions On A Unix Server

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