Java Socket Client-Server中的“主机连接丢失”

Question

For the server I have to alter the provided code into a multi-threaded server. For the client I have alter to it to make it read data from a text file.

So far I've managed to compile but when running on the client side it not only gives odd symbols but in the end it says "connection host lost". I've tried changing the socket number the same problem persists.

So this is what it looks like:

¼Ýsr♥Car´3▼3çw3û☻♦DmileageLmodelt↕Ljava/lang/String;Lownerq~☺L

registrationq~☺xp@ "Honda Civic""John S"q~sq~@@t-sq~@Òêt "Vokswagen"t "Maria B"q~

Connection to host lost.

This is my code for server:

//a simple client/server application: car registration
//a SERVER program that uses a stream socket connection to exchange objects

import java.net.*;
import java.io.*;

public class CarsServer {

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

    ServerSocket serverSocket = null;; // TCP socket used for listening

    try {
      /* step 1: create a server socket port number: 8000 */
      serverSocket = new ServerSocket(5200);
      int i = 0;

      for(;;){
        /* setp 2: listen for a connection and create a socket */

        System.out.println("*** this server is going to register the cars ***");
        System.out.println("listening for a connection...");

        Socket clientSocket = serverSocket.accept();
        System.out.println("Spawning " + i++);
        new CarsClient(clientSocket, i).start();
      }
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        /* step 5: close the connection to the client */
        System.out.println("*** the server is going to stop running ***");
        serverSocket.close();
    }
  }
}

And for Client

//a simple client/server application that exchanges OBJECTS
//a CLIENT program that uses a stream socket connection to exchange objects

import java.net.*;
import java.io.*;

class CarsClient extends Thread{

    private Socket incoming;
    private int client;

    public CarsClient(Socket i, int c){
        this.client = c;
        this.incoming = i;
    }

    public void run(){
        try {
          /*
           * step 2: connect input and output streams to the socket
           */
          BufferedReader oisFromServer = new BufferedReader(new FileReader("Cars.txt"));

          ObjectOutputStream oosToServer = new ObjectOutputStream(incoming.getOutputStream());

          System.out.println("I/O streams connected to the socket");

      /*
       * step 3: communicate with the server
       */
        Car[] cars = new Car[3];
        int n = 0;
        String[] l;
        String line;
        while((line = oisFromServer.readLine()) != null){
           l = line.split(", ");
            try {
                // receive an object from the server
                cars[n] = new Car(l[0], l[1], Integer.parseInt(l[2])); // casting!

                // send an object to the server
                oosToServer.writeObject(cars[n]);
                //oosToServer.flush();
                System.out.println("\n### send this car to the server for registration:\n" + cars[n]);

                System.out.println("\t###### the car returned by the server:\n"+ cars[n]);
                n++;
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                }
            } catch (EOFException eof) {
                System.out.println("The server has terminated connection!");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
          /*
           * step 4: close the connection to the server
           */
          System.out.println("\nClient: closing the connection...");
          oosToServer.close();
          oisFromServer.close();
          incoming.close();
        } catch (IOException ioe) {
          ioe.printStackTrace();
        }
        System.out.println("the client is going to stop runing...");
    } // end run
}

I'm new to programming so please help me out.

Answer 1

It appears that your issue is here:

while((line = oisFromServer.readLine()) != null){

You are consuming all the lines of text, and once that's done, oisFromServer is going to return null.

To solve this, I recommend you use the raw InputStream and InputStream.read() from the socket. Also, once upon a time I wrote a utility class for this kind of blocking reading. See DataFetcher , and its dependencies in the same project package