How to implement a Java file resume?

Question

Java

There is a client-server program with a typical file transfer in pieces through sockets

while ((bytesRead = in.read(mybytearray, 0, mybytearray.length)) != -1) {
                bos.write(mybytearray, 0, bytesRead);
            }

The full code can be viewed here .
There is data on which place the download was interrupted, that is, how much was downloaded, how to make the program "download" the file from that very place? For example, there is a file weighing 33345 bytes, during the jump there was a break and 25000 bytes were downloaded, how to make the program start downloading this file from 25000 bytes? I don't know where to pass this number.

Answer 1

Already suggested, here is the answer

Answer 2

greenbytes.de/tech/webdav/draft-ietf-httpbis-p5-ra...