How to send and receive serialized object in socket channel

Question

I want to transmit a serialized object over a socket channel. I want make "Hi friend" string as serialized object and then write this object in socket channel while in the other end i want to read the same object and retrieve the data.

All these things I want to do using Java SocketChannel. How to do this? I have tried like below, but did not get any data in the recipient side.

private static void writeObject(Object obj, SelectionKey selectionKey) {
    ObjectOutputStream oos;
    try {
        SocketChannel channel = (SocketChannel) selectionKey.channel();
        oos = new ObjectOutputStream(Channels.newOutputStream(channel));

        oos.writeObject(obj);
    } catch (IOException ex) {
        ex.printStackTrace();
    }
}

private static Object readObject(SelectionKey selectionKey) {
    ObjectInputStream ois;
    Object obj = new Object();
    SocketChannel channel = (SocketChannel) selectionKey.channel();
    try {
        ois = new ObjectInputStream(Channels.newInputStream(channel));
        obj = ois.readObject();
    } catch (Exception ex) {
        ex.printStackTrace();
    }
    return obj;
}

Answer 1

Your SocketChannel handling seems to be incomplete, see this complete example for SocketChannels transferring a byte:

/*
 * Writer
 */
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.net.InetSocketAddress;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;

public class Sender {
    public static void main(String[] args) throws IOException {
     System.out.println("Sender Start");

     ServerSocketChannel ssChannel = ServerSocketChannel.open();
     ssChannel.configureBlocking(true);
     int port = 12345;
     ssChannel.socket().bind(new InetSocketAddress(port));

     String obj ="testtext";
     while (true) {
      SocketChannel sChannel = ssChannel.accept();

      ObjectOutputStream  oos = new 
                      ObjectOutputStream(sChannel.socket().getOutputStream());
      oos.writeObject(obj);
      oos.close();

      System.out.println("Connection ended");
     }
    }
}

And the Reader

/*
 * Reader
 */
import java.io.IOException;
import java.io.ObjectInputStream;
import java.net.InetSocketAddress;
import java.nio.channels.SocketChannel;

public class Receiver {
    public static void main(String[] args) 
    throws IOException, ClassNotFoundException {
     System.out.println("Receiver Start");

     SocketChannel sChannel = SocketChannel.open();
     sChannel.configureBlocking(true);
     if (sChannel.connect(new InetSocketAddress("localhost", 12345))) {

      ObjectInputStream ois = 
                     new ObjectInputStream(sChannel.socket().getInputStream());

      String s = (String)ois.readObject();
      System.out.println("String is: '" + s + "'");
     }

     System.out.println("End Receiver");
    }
}

When you first start the Server and than the Receiver, you'll get the following output:

Server's console

Sender Start
Connection ended

Receiver's console

Receiver Start
String is: 'testtext'
End Receiver

This is not the best solution, but follows your use of Java's ServerSocketChannel