This is a challenge if you plan on sending zero bytes. It will stop at the first zero byte. It transmits a zero terminated string.
Udp.beginPacket(remote_ip, remote_port);
Udp.write(ReplyBuffer);
Udp.endPacket();
If you want to send zero bytes, you need something like this:
Udp.beginPacket(remote_ip, remote_port);
Udp.write(ReplyBuffer,20);
Udp.endPacket();
This sends 20 bytes, zeros and all.