How to make the simplest Client-server in java to transfer a file via ftp?

Question

Java

It is necessary to write the simplest client and server. The bottom line is that the client sends a file, and the server receives it and saves it. It's all organized through the ftp protocol. How can I do that? With difficulty, I made a transfer by bytes (I read the file into an array of bytes and transfer it to the server), but this is not quite right. I just started learning a programming language, if it's not difficult, please explain in detail.
Thank you.

Answer 1

Use this to transfer files
If you're writing both client and server parts from scratch, might REST be better ?
Github
By FTP