* added sample file to transfer
* split client and server into separate files
* client and server now work in python2
* server works on python3
* client works on python3
* allow configurable ONE_CONNECTION_ONLY for testing server
* allow testing of ftp server + client
* use f-strings
* removed single letter vars
* fixed bad quote marks
* clearer file handler names
* 'with open() as' syntax
* unicode and emojis in the test data
* s -> sock
* consistent comment spacing
* remove closing formalities
* swap in and out_file
* f-string
* if __name__ == '__main__':
