Example of how to send an Object over a Socket in Java.

SendObjectsOverSockets.java

import java.io.Serializable;

// must implement Serializable in order to be sent
public class Message implements Serializable{
    private final String text;

    public Message(String text) {
        this.text = text;
    }

    public String getText() {
        return text;
    }
}

import java.io.*;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;

public class Client {

    public static void main(String[] args) throws IOException {
        // need host and port, we want to connect to the ServerSocket at port 7777
        Socket socket = new Socket("localhost", 7777);
        System.out.println("Connected!");

        // get the output stream from the socket.
        OutputStream outputStream = socket.getOutputStream();
        // create an object output stream from the output stream so we can send an object through it
        ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream);

        // make a bunch of messages to send.
        List<Message> messages = new ArrayList<>();
        messages.add(new Message("Hello from the other side!"));
        messages.add(new Message("How are you doing?"));
        messages.add(new Message("What time is it?"));
        messages.add(new Message("Hi hi hi hi."));

        System.out.println("Sending messages to the ServerSocket");
        objectOutputStream.writeObject(messages);

        System.out.println("Closing socket and terminating program.");
        socket.close();
    }
}


import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.List;

public class Server {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        // don't need to specify a hostname, it will be the current machine
        ServerSocket ss = new ServerSocket(7777);
        System.out.println("ServerSocket awaiting connections...");
        Socket socket = ss.accept(); // blocking call, this will wait until a connection is attempted on this port.
        System.out.println("Connection from " + socket + "!");

        // get the input stream from the connected socket
        InputStream inputStream = socket.getInputStream();
        // create a DataInputStream so we can read data from it.
        ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);

        // read the list of messages from the socket
        List<Message> listOfMessages = (List<Message>) objectInputStream.readObject();
        System.out.println("Received [" + listOfMessages.size() + "] messages from: " + socket);
        // print out the text of every message
        System.out.println("All messages:");
        listOfMessages.forEach((msg)-> System.out.println(msg.getText()));

        System.out.println("Closing sockets.");
        ss.close();
        socket.close();
    }
}

// Server output
/*
ServerSocket awaiting connections...
Connection from Socket[addr=/127.0.0.1,port=62360,localport=7777]!
Received [4] messages from: Socket[addr=/127.0.0.1,port=62360,localport=7777]
All messages:
Hello from the other side!
How are you doing?
What time is it?
Hi hi hi hi.
Closing sockets.
*/

// Client output
/*
Connected!
Sending messages to the ServerSocket
Closing socket and terminating program.
*/

this is absolutely working for me

Is working

Thank you... It's work

Thank you ...

Just curious, 'msg' isn't defined so that was confusing.

Hello guys! Thanks for your code. But I want create 1 server and two client. One client is supported publish message, other client is supported receive message. But when I run server, I can only run 1 client connected to it.

Thank you! The code was useful to me.

Thanks, this was really useful!

Hi! It worked, kudos

@trinhvandat You would need to create 2 Sockets in your Server class so that it can handle 2 clients connecting to it. In general, in your server class, you should create as many Sockets as there are clients that are going to be connecting to it.

thank u bro

what if I want to send more than one variable from the object class?
what must I do

and are these classes in different projects? or are in one project?