In order to establish a connection - there needs to be a 1) sender (server) (the owner of the file), waiting for connections, and a 2) receiver (client), who will try to connect to a sender (server). If the requirements are met - client will connect to server and the packet exchange will begin.
The server and the client needs to communicate with packets according to certain rules, given by a [protocol](http://unbewohnte.xyz:3000/Unbewohnte/ftu/src/branch/main/src/protocol).
The packet has its header and body. They are divided into several groups of use by headers, this way we can specify what kind of data is stored inside packet`s body and react accordingly.
Thus, with a connection and a way of communication, the sender will send some packets with necessary information about the file to the receiver that describe a filename, its size and a checksum. The client (receiver) will have the choice of accepting or rejecting the packet. If rejected - the connection will be closed and the program will exit. If accepted - the file will be transferred via packets.