How to send and receive serialized object in socket channel

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, then 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