Echo Server in Java

EchoServer.java

package com.manzanit0;

import java.io.*;
import java.net.ServerSocket;

public class EchoServer {
    public static void main(String[] args) {
        int portNumber = 4098;

        try (
                var serverSocket = new ServerSocket(portNumber);
                var clientSocket = serverSocket.accept();
                var outputStream = clientSocket.getOutputStream();
                var inputStream = clientSocket.getInputStream()
        ) {
            while(true) {
                var bytes = readAllBytes(inputStream);
                outputStream.write(bytes);
            }

        } catch (IOException e) {
            System.out.println(e.getMessage());
        }
    }

    private static byte[] readAllBytes(InputStream stream) throws IOException {
        StringBuilder data = new StringBuilder();

        // available only returns a value after reading at least 1 character -> do/while.
        do {
            data.append((char) stream.read());
        } while (stream.available() > 0);

        return data.toString().getBytes();
    }
}