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 - a client will connect to a 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](https://github.com/Unbewohnte/FTU/tree/main/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.
-`-sending` (bool) - if true - creates a server (sender) (also need to provide a `-sharefile` flag in that case), if false - creates a client (receiver)
-`-port` (int) - specifies a port; if `-sending` == true - listens on that port, else - connects to given port
-`addr` (string) - specifies an address to connect to (used when `-sending=false`)
-`-sharefile` (string) - specifies path to a file you want to share (used in pair with `-sending=true`), if given a valid path - a server will offer to share this file to a client
-`./FTU -sending=false -downloadto="/home/some_path_here/Downloads/" -addr="192.168.1.104"` - creates a client (receiver) that will try to connect to `192.168.1.104` (local device) on port `8080` and if successful - downloads a file to given path
-`./FTU -sending=false -downloadto="/home/some_path_here/Downloads/" -addr=145.125.53.212 -port=8888` - same as before, but will try to connect to `145.125.53.212` on port `8888`
- **VERY** slow; somewhat FIXED - [x], now **a little** faster than before
- **VERY** expensive on resources; somewhat FIXED - [x], no more **json manipulations**, only **raw bytes**`s wizardry !
- If `MAXFILEDATASIZE` is bigger than appr. 1024 - the packets on the other end will not be unmarshalled due to error ??; FIXED - [x], unnecessary, wrong, deprecated, **destroyed !!!** (But now present in the other form, unfortunately)
This is NOT intended to be a serious application. I'm learning and this is a product of my curiosity. If you're a beginner too, please don't try to find something useful in my code, I am not an expert.
Also, this utility only works if both the server and the client have a port-forwarding enabled and configured. Fortunatelly, locally it works without any port-forwarding.
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## Inspired by [croc](https://github.com/schollz/croc)
