如何使用 Java 中的套接字访问客户端 - 服务器架构中的文件？

Question

I need to read a "bdd.txt" file placed on a Virtual Machine on my computer. I made a client/server system in Java. My Server.java is on my VM (Ubuntu) with a "database" (the bdd.txt file in the same folder), and my Client.java is on my Windows 7.

So far I have split my code into 2 different files (Server/Client) and I made the connexion between my Windows 7 and my VMware Player's Ubuntu. When I start my server on my VM, it listens on a port number x, then I go back on my Windows and run my client. It asks to make the connexion and then, back on my VM, I print a message "The connexion is made" and my app is running. So now I can communicate between them. I have just used socket = new Socket("my VM ip address",portNumber); and it works. But now, I have no idea how to adapt my code to reach my bdd.txt file I moved on my VM.

How can I now read the bdd.txt file, to have access to the pin codes ? Why is my new Client() never called in my program?

Here is Client.java :

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.util.Scanner;


public class Client {
    public static void main(String[] args) throws IOException {

        int pinSize = 0;

          //set up server communication
          Socket clientSocket = new Socket(InetAddress.getLocalHost(),1234);
          BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
          PrintWriter out = new PrintWriter(clientSocket.getOutputStream());

          Scanner scanner = new Scanner(System.in);
          System.out.println("Enter pin : ");
          String password = scanner.next();
          pinSize = password.length();

          //send PIN to server
          out.println(password);

          if (pinSize != 4) { 
      System.out.println("Pin must be 4 digits");
    } else {
      System.out.println("Checking...");
    }

          out.flush();

          //get response from server
          String response = in.readLine();
          System.out.println(response);

          in.close();
          out.close();
          clientSocket.close();
        }
}

Here is Server.java (in the same folder as bdd.txt):

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;


public class Server {

    private static ServerSocket server;

    public static void main(String[] args) throws Exception {

          server = new ServerSocket(1234);
          Socket socket = server.accept();      
          BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
          PrintWriter out = new PrintWriter(socket.getOutputStream());

          //Listen for client requests:
          String request;
          while ((request = in.readLine()) != null) {

            //check PIN, send result
            boolean pinCorrect = checkPin(request);
            out.println(pinCorrect ? "yes" : "no");
            out.flush();
          }

          out.close();
          in.close();
          socket.close();
        }

        /**
         * Check if PIN is in bdd.txt
         * @throws IOException 
         */
        private static boolean checkPin(String pin) throws IOException {
          boolean result = false;
          File file = new File("bdd.txt");
          BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream(file)));
          String line;
          while ((line = in.readLine()) != null) {
            result |= (line.equals(pin));
          }
          in.close();
          return result;
        }
}

Answer 1

There's a lot of irrelevant stuff in you question, it's hard to see how your program works.

Here's what should happen:

Client side:

• User inputs a number
• Client sends user's number to server
• Client receives response from server, and displays it

Server side:

• Server listens for client connection
• Server receives number from client
• Server checks number against file bbd.txt
• If number exists in file, return yes else return no

I have written some simple code to show you, excluding UI stuff:

Client.java:

public static void main(String[] args) {

  //set up server communication
  Socket clientSocket = new Socket("ip.address",1234);
  BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
  PrintWriter out = new PrintWriter(socket.getOutputStream());


  //send PIN to server
  out.println("9.8.7.6");
  out.flush;

  //get response from server
  String response = in.readLine();
  System.out.println(response);

  in.close();
  out.close();
  clientSocket.close();
}

Server.java:

public static void main(String[] args) throws Exception {

  //Set up client communication
  ServerSocket server = new ServerSocket(1234);
  Socket socket = server.accept();      
  BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
  PrintWriter out = new PrintWriter(socket.getOutputStream());

  //Listen for client requests:
  String request;
  while ((request = in.readLine()) != null) {

    //check PIN, send result
    boolean pinCorrect = checkPin(request);
    out.println(pinCorrect ? "yes" : "no");
    out.flush();
  }

  out.close();
  in.close();
  socket.close();
}

/**
 * Check if PIN is in bdd.txt
 */
private static boolean checkPin(String pin) {
  boolean result = false;
  File file = new File("bdd.txt");
  BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream(file)));
  String line;
  while ((line = in.readLine()) != null) {
    result |= (line.equals(pin));
  }
  in.close();
  return result;
}