import java.io.*; 
 
import java.net.*; 
 
import java.util.StringTokenizer; 
 
 
 
/** 
 
 * A Web proxy server which is both a client and a server at the same time. 
 
 *  
 
 * @author shapeng 053704
 
 */ 
 
 
 
public class WebProxyServer { 
 
 
 
  public WebProxyServer() throws Exception { 
 
 
 
    /* the server socket */ 
 
    ServerSocket serSk = new ServerSocket(8080); 
 
 
 
    /* the counter of clients */ 
 
    int counter = 1; 
 
 
 
    while (true) { 
 
      Socket cliSk = serSk.accept(); 
 
      System.out.println("Accepting Client " + counter 
 
          + "'s Connection...\n"); 
 
 
 
      /* a thread for a client */ 
 
      ServerThread st = new ServerThread(cliSk, counter++); 
 
      st.start(); 
 
    } 
 
  } 
 
 
 
  class ServerThread extends Thread { 
 
 
 
    /* a client socket */ 
 
    private Socket sk; 
 
 
 
    /* the counter of clients */ 
 
    private int counter; 
 
 
 
    ServerThread(Socket sk, int counter) { 
 
      this.sk = sk; 
 
      this.counter = counter; 
 
    } 
 
 
 
    public void run() { 
 
 
 
      /* reader and writer */ 
 
      BufferedReader inFromClient = null; 
 
      DataInputStream inFromServer = null; 
 
      DataOutputStream outToClient = null; 
 
      DataOutputStream outToServer = null; 
 
 
 
      /* response the request */ 
 
      try { 
 
        while (true) { 
 
 
 
          /* Reader and writer between proxy server and client */ 
 
          inFromClient = new BufferedReader(new InputStreamReader(sk 
 
              .getInputStream())); 
 
          outToClient = new DataOutputStream(sk.getOutputStream()); 
 
 
 
          System.out.println("Waiting for Client " + counter 
 
              + "\'s command..."); 
 
          String cmd = inFromClient.readLine(); 
 
          System.out.println("The Client " + counter 
 
              + " request for: " + cmd); 
 
 
 
          /* 
 
           * Process the command from client and identify the method 
 
           * and address. If command error, write the error response 
 
           * and break. 
 
           *  
 
           */ 
 
          StringTokenizer token = new StringTokenizer(cmd); 
 
          if (token.countTokens() < 2) { 
 
 
 
            System.out.println("Command style error!"); 
 
            outToClient.writeBytes("HTTP/1.1 400 Bad Request\n\r"); 
 
            break; 
 
 
 
          } else { 
 
 
 
            String method = token.nextToken(); 
 
            String url = token.nextToken(); 
 
 
 
            if (!method.equals("GET")) { 
 
              System.out.println("method error!"); 
 
              System.out.println("HTTP/1.1 400 Bad Request\n\r"); 
 
              break; 
 
            } 
 
 
 
            if (!url.toUpperCase().startsWith("HTTP://")) { 
 
              System.out.println("url error!"); 
 
              System.out.println("HTTP/1.1 400 Bad Request\n\r"); 
 
              break; 
 
            } 
 
 
 
            /* 
 
             * process the file name and make sure the server name, 
 
             * the file path and the number of port. 
 
             */ 
 
            int port = 0; 
 
            int strIndex = 0; 
 
            String serverName = ""; 
 
            String portToString = ""; 
 
            String filePath = ""; 
 
 
 
            url = url.substring(7); 
 
            strIndex = url.indexOf("/"); 
 
            serverName = url.substring(0, url.indexOf("/")); 
 
            filePath = url.substring(url.indexOf("/")); 
 
 
 
            if (serverName.contains(":")) { 
 
              strIndex = serverName.indexOf(":"); 
 
              portToString = serverName.substring(strIndex + 1); 
 
              serverName = serverName.substring(0, strIndex); 
 
            } else { 
 
              portToString = "80"; 
 
            } 
 
 
 
            port = Integer.parseInt(portToString); 
 
 
 
            /* 
 
             * Response the right format request. Identify the file 
 
             * tpye and write it to the client. 
 
             *  
 
             */ 
 
            System.out.println(serverName); 
 
            System.out.println(port); 
 
            System.out.println(filePath); 
 
            System.out.println(url); 
 
            System.out.println("Now respond the Client " + counter 
 
                + "\'s request..."); 
 
 
 
            /* the client socket */ 
 
            Socket clientSocket = new Socket(serverName, port); 
 
 
 
            /* Reader and writer between proxy server and server */ 
 
            inFromServer = new DataInputStream(clientSocket 
 
                .getInputStream()); 
 
            outToServer = new DataOutputStream(clientSocket 
 
                .getOutputStream()); 
 
 
 
            outToServer.writeBytes("GET " + filePath 
 
                + " HTTP/1.0\r\n\r\n"); 
 
 
 
            /* read from server and write to client */ 
 
            String response = inFromServer.readLine(); 
 
 
 
            while (!response.equals("")) { 
 
 
 
              response = inFromServer.readLine(); 
 
            } 
 
 
 
            byte[] bytes = new byte[1024]; 
 
 
 
            int size = 0; 
 
 
 
            while ((size = inFromServer.read(bytes, 0, 1024)) != -1) { 
 
 
 
              outToClient.write(bytes, 0, size); 
 
            } 
 
            break; 
 
          } 
 
        } 
 
 
 
      } catch (Exception e) { 
 
        e.printStackTrace(); 
 
      } finally { 
 
 
 
        /* 
 
         * Close the reader, writer and client socket. 
 
         *  
 
         */ 
 
        System.out.println("Closing Client " + counter 
 
            + "\'s Connection...\n"); 
 
 
 
        try { 
 
          if (inFromClient != null) 
 
            inFromClient.close(); 
 
          if (outToClient != null) 
 
            outToClient.close(); 
 
          if (inFromServer != null) 
 
            inFromServer.close(); 
 
          if (outToServer != null) 
 
            outToServer.close(); 
 
          if (sk != null) 
 
            sk.close(); 
 
        } catch (IOException e) { 
 
        } 
 
      } 
 
    } 
 
  } 
 
 
 
  public static void main(String[] args) { 
 
 
 
    try { 
 
      WebProxyServer pServer = new WebProxyServer(); 
 
 
 
    } catch (Exception e) { 
 
 
 
      e.printStackTrace(); 
 
    } 
 
 
 
  } 
 
}