I am not sure if your ops is set correctly. If that socket is used to listening, you may need to set it as SelectionKey.OP_ACCEPT, and read data as SelectionKey.OP_READ. https://github.com/harleyw/NioSocketLib/ could be referred for Java nio socket.

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Date;
import java.util.Iterator;
import java.util.Set;

public class NIOServer {
    private static Selector selector = null;

    public static void main(String[] args)
    {

        try {
            selector = Selector.open();
            // We have to set connection host,port and
            // non-blocking mode
            ServerSocketChannel serverSocketChannel
                    = ServerSocketChannel.open();
            ServerSocket serverSocket
                    = serverSocketChannel.socket();
            serverSocket.bind(
                    new InetSocketAddress("localhost", 8089));
            serverSocketChannel.configureBlocking(false);
            int ops = serverSocketChannel.validOps();  <<<<<<<<<<<<<<<
            serverSocketChannel.register(selector, ops,
                    null);
            while (true) {
                selector.select();
                Set<SelectionKey> selectedKeys
                        = selector.selectedKeys();
                Iterator<SelectionKey> i
                        = selectedKeys.iterator();

                while (i.hasNext()) {
                    SelectionKey key = i.next();

                    if (key.isAcceptable()) {
                        // New client has been accepted
                        handleAccept(serverSocketChannel,
                                key);
                    }
                    else if (key.isReadable()) {
                        // We can run non-blocking operation
                        // READ on our client
                        handleRead(key);
                    }
                    i.remove();
                }
            }
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }