为什么以下代码会命中IOException？

Question

Client Class

import java.io.PrintWriter;
import java.net.Socket;

public class Client 
{
    public static void main(String[] args) 
    {
        try 
        {
            System.out.println(" Starting Client ");
            Socket socket = new Socket ("localhost",55555);
        PrintWriter printWriter = new PrintWriter(socket.getOutputStream(),true);
            printWriter.println("Hello from client");
            printWriter.println("Conected, Yes!");
            socket.close();// Changes as suggested by Jack
        } 
        catch (Exception e) 
        {
            System.out.println(e);
        }


    }
}

Server Class

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;

public class Server 
{
    public static void main(String[] args)
    {
        System.out.println(" inside main ");
        try 
        {
            System.out.println("Starting Server");
            ServerSocket serverSocket= new ServerSocket(55555);
            Socket clientSocket = serverSocket.accept();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
            String inputLine;
            while ((inputLine= bufferedReader.readLine())!=null) 
            System.out.println("Server Message:"+inputLine);

        } 
        catch (IOException e) 
        {
            System.out.println("IOException "+e);
        }
    }
}

Output:
Starting Server
Server Message:Hello from client
Server Message:Conected, Yes!
IOException java.net.SocketException: Connection reset

Client and Server java files are in the same package. What would trigger IOException in the following code? Is it something to do with Eclipse? FYI, I am using Eclipse SDK Version: 4.2.2 Build id: M20130204-1200

Answer 1

The problem is that your client opens a Socket , sends some data and then exits the program, thus abruptly closing the connection.

You should call close() on the Socket from the client side to notify the server that the socket it is going to be closed.

Answer 2

As @Jack mentioned in his answer you need to close() your socket before the client application exit.

Socket is AutoCloseable

The safe way of work with closable resource is creation in try block:

public class Client {
    public static void main(String[] args) {
            System.out.println(" Starting Client ");
            try(Socket socket = new Socket("localhost", 55555)) {
                PrintWriter printWriter = new PrintWriter(socket.getOutputStream(), true);
                printWriter.println("Hello from client");
                printWriter.println("Conected, Yes!");
            } catch (IOException e) {
                e.printStackTrace();
            }
    }
}

and it will be closed automatically on exit (from try section).