NioServer and NioClient

NioServer server = new NioServer(8080);
server.setChannelHandler((sc)->{
    ByteBuffer readBuffer = ByteBuffer.allocate(1024);
    try{
        // Read data from the channel to the buffer
        int readBytes = sc.read(readBuffer);
        if (readBytes > 0) {
            // Flips this buffer.  The limit is set to the current position and then
            // the position is set to zero, indicating that data should be read from the beginning.
            readBuffer.flip();
            // Returns the number of elements between the current position and the  limit.
            // The length of bytes to be read.
            byte[] bytes = new byte[readBuffer.remaining()];
            // Read data from the buffer to the bytes array.
            readBuffer.get(bytes);
            String body = StrUtil.utf8Str(bytes);
            Console.log("[{}]: {}", sc.getRemoteAddress(), body);
            doWrite(sc, body);
        } else if (readBytes < 0) {
            IoUtil.close(sc);
        }
    } catch (IOException e){
        throw new IORuntimeException(e);
    }
});
server.listen();

public static void doWrite(SocketChannel channel, String response) throws IOException {
    response = "Received message: " + response;
    // Write buffer data to the channel and send it back to the client.
    channel.write(BufferUtil.createUtf8(response));
}

NioClient client = new NioClient("127.0.0.1", 8080);
client.setChannelHandler((sc)->{
    ByteBuffer readBuffer = ByteBuffer.allocate(1024);
    // Read data from the channel to the buffer
    int readBytes = sc.read(readBuffer);
    if (readBytes > 0) {
        // Flips this buffer.  The limit is set to the current position and then
        // the position is set to zero, indicating that data should be read from the beginning.
        readBuffer.flip();
        // Returns the number of elements between the current position and the  limit.
        // The length of bytes to be read.
        byte[] bytes = new byte[readBuffer.remaining()];
        // Read data from the buffer to the bytes array.
        readBuffer.get(bytes);
        String body = StrUtil.utf8Str(bytes);
        Console.log("[{}]: {}", sc.getRemoteAddress(), body);
    } else if (readBytes < 0) {
        sc.close();
    }
});
client.listen();
client.write(BufferUtil.createUtf8("Hello.\n"));
client.write(BufferUtil.createUtf8("Hello2."));
// Send data to the server from the console
Console.log("Please enter a message to send:");
Scanner scanner = new Scanner(System.in);
while (scanner.hasNextLine()) {
    String request = scanner.nextLine();
    if (request != null && request.trim().length() > 0) {
        client.write(BufferUtil.createUtf8(request));
    }
}