server.java

一个简单的代理服务器

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

public class Server implements java.lang.Runnable {
	static int serverSocketPort = 8000;

	/**
	 * userSocket represent the socket connect to the user
	 */
	private Socket userSocket;		

	/**
	 * serverSocket represent the socket connect to the server
	 */
	static Socket serverSocket;

	static String commandFromUser = "";

	static String serverName = "";

	static String fileLocation = "";

	static String httpType = "";

	static int portNum = 80;

	/**
	 * Constructor
	 * 
	 * @param socket
	 */
	public Server(Socket socket) {
		userSocket = socket;
	}

	/**
	 * The main function
	 * 
	 * @param argv
	 * @throws IOException
	 */
	public static void main(String argv[]) throws IOException {
		ServerSocket listenSocket = new ServerSocket(serverSocketPort);
		while (true) {
			Runnable run = new Server(listenSocket.accept());
			Thread threadServer = new Thread(run);
			threadServer.start();
		}
	}

	public void run() {
		try {
			String totalCommand = getCommandFromUser(); // Get all infomation of
														// the input from the user
			StringTokenizer tokenizedLine = new StringTokenizer(totalCommand);
			String command = tokenizedLine.nextToken();
			if (command.equals("GET") && tokenizedLine.hasMoreTokens()) {
				get(totalCommand); // If the command is a Right command, analyse the total command

				System.out.println("The user want to get info form : \n"
						+ serverName + fileLocation + " at port " + portNum);
				serverSocket = new Socket(serverName, portNum);		//Create a new socket to connect with the server
				DataOutputStream outToServer = new DataOutputStream(
						serverSocket.getOutputStream());
				String commandToServer = commandFromUser + " " + fileLocation
						+ " " + httpType + "\r\n\r\n";
				outToServer.writeBytes(commandToServer);			//Send the user's command to the server
				System.out.println("The command is: " + commandToServer);
				BufferedReader inFromServer = new BufferedReader(
						new InputStreamReader(serverSocket.getInputStream()));
				String infoFromServer = inFromServer.readLine();
				String totalInfo = "";
				while (infoFromServer != null && !infoFromServer.isEmpty()) {		//Get all informaiton sent by the server
					totalInfo += infoFromServer;
					infoFromServer = inFromServer.readLine();
				}
				System.out.println(totalInfo);
				DataOutputStream outToClient = new DataOutputStream(userSocket
						.getOutputStream());
				outToClient.writeBytes(totalInfo);			//Send the received information to the user
				outToClient.close();
			} else{
				wrongCommand();
			}
			userSocket.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	/**
	 * Get the user's command 
	 * @return the total information getted from the user
	 * @throws IOException
	 */
	private String getCommandFromUser() throws IOException {
		System.out.println(userSocket.getInetAddress() + "    is connected");
		BufferedReader inFromClient = new BufferedReader(new InputStreamReader(
				userSocket.getInputStream()));
		String clientCommand = inFromClient.readLine();
		String totalCommand = "";
		while (clientCommand != null && !clientCommand.isEmpty()) {
			totalCommand += clientCommand + "\r\n";
			clientCommand = inFromClient.readLine();
		}
		return totalCommand;
	}

	/**
	 * Analyse the user's input command
	 * @param totalCommand 
	 * the user's all input
	 */
	private void get(String totalCommand) {
		StringTokenizer tocken = new StringTokenizer(totalCommand);
		commandFromUser = tocken.nextToken();		//Get command "GET"
		String totalURL = tocken.nextToken();
		httpType = tocken.nextToken();				//Get http type like "HTTP/1.0"
		String httpHead = "http://";
		StringTokenizer urlToken = new StringTokenizer(totalURL
				.substring(httpHead.length()), ":");
		serverName = urlToken.nextToken();			//Get server's name
		if (urlToken.hasMoreTokens()) {				//if the user input the port number
			String portString = urlToken.nextToken();
			StringTokenizer portToken = new StringTokenizer(portString, "/");
			portNum = Integer.parseInt(portToken.nextToken());
			fileLocation = "/" + portToken.nextToken();
		} else {									//if the user does not input the port number
			StringTokenizer nameToken = new StringTokenizer(serverName, "/");
			serverName = nameToken.nextToken();
			portNum = 80;
			fileLocation = "/" + nameToken.nextToken();
		}
	}
	
	/**
	 * if the user does not input a right command
	 * @throws IOException
	 */
	private void wrongCommand() throws IOException {
		DataOutputStream outToClient = new DataOutputStream(userSocket
				.getOutputStream());
		String totalInfo = "Wrong command";
		outToClient.writeBytes(totalInfo);
	}
}