import org.lavajuno.jfskmodem.Transmitter;

import java.nio.charset.StandardCharsets;

public static void main(String[] args) {
    Transmitter t = new Transmitter(1200);
    String s = "Hello world!";
    t.transmit(s.getBytes(StandardCharsets.UTF_8));
}

import org.lavajuno.jfskmodem.Receiver;

import java.nio.charset.StandardCharsets;

public static void main(String[] args) {
    Receiver r = new Receiver(1200);
    byte[] b = r.receive(100);
    System.out.println(new String(b, StandardCharsets.UTF_8));
}