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 probablyInternet 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. Sincethe 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);

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