Connection refused from client to server

Question

I am learning about Sockets in Java and I am only missing how to receive back response from the server.

Following How to send string array object and How to send and receive serialized object in socket channel, I am trying to ask the user to pick as much as he wants out of choices:

1 - 2 - 3 - 4

And then I want to split and send them as an array to a server, where the server should send back the number of choices the user has picked.

For example if the user chose

2 3 4 1 2 3 4 1

Server should return

8

server is sending response fine, but on the client side I get error:

Exception in thread "main" java.net.ConnectException: Connection refused: connect at java.net.DualStackPlainSocketImpl.connect0(Native Method) at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source) at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source) at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source) at java.net.AbstractPlainSocketImpl.connect(Unknown Source) at java.net.PlainSocketImpl.connect(Unknown Source) at java.net.SocksSocketImpl.connect(Unknown Source) at java.net.Socket.connect(Unknown Source) at java.net.Socket.connect(Unknown Source) at java.net.Socket.(Unknown Source) at java.net.Socket.(Unknown Source) at ClientClass.main(ClientClass.java:26)

I am not sure why the issue. Any help?

My Client:

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Scanner;

public class ClientClass {

    public static void main(String args[]) throws IOException, ClassNotFoundException 
    {
        // take order and convert it to array of choices
        Scanner myScanner = new Scanner(System.in); // take from user
        System.out.println("Enter all your choices seperated by space:");
        System.out.println("Choices are: 1- 2- 3- 4");
        String orderString = myScanner.next();
        orderString += myScanner.nextLine();
        String orderArray[] = orderString.split(" ");

        // send request to server
        Socket mySocket = new Socket("127.0.0.1", 4444); // create a socket
        ObjectOutputStream out = new ObjectOutputStream(mySocket.getOutputStream());
        out.writeObject(orderArray);  

       // get response from server
       InputStream is = mySocket.getInputStream();
       InputStreamReader isr = new InputStreamReader(is);
       BufferedReader br = new BufferedReader(isr);
       String message = br.readLine();
       System.out.println("Message received from the server : " +message);

    }
}

My Server:

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.PrintStream;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.channels.SocketChannel;
import java.util.Scanner;

public class ServerClass {

    public static void main(String args[]) throws IOException, ClassNotFoundException
    {
        // receive
        ServerSocket myServerSocket = new ServerSocket(4444); // create a server socket
        Socket mySimpleSocket = myServerSocket.accept(); // accept requests
        ObjectInputStream ois = new ObjectInputStream(mySimpleSocket.getInputStream());
        String[] choices = (String[]) ois.readObject();


       // send back response
       OutputStream os = mySimpleSocket.getOutputStream();
       OutputStreamWriter osw = new OutputStreamWriter(os);
       BufferedWriter bw = new BufferedWriter(osw);
       bw.write(choices.length);
       System.out.println("Message sent to the client is "+choices.length);
       bw.flush();

    }
}

score 0 · Accepted Answer · answered Oct 19 '17 at 23:56

server is sending response fine

Rubbish. The server isn't even getting an incoming connection, let alone reading the request, let alone sending a response.

but on the client side I get error:

Exception in thread "main" java.net.ConnectException: Connection refused: connect at

On this evidence the server wasn't even running. Certainly not running in the same host as the client, which is what is required by new Socket("127.0.0.1", 4444).

Connection refused from client to server

1 Answers1