Super simple asynchronous FTP server with pyftpdlib

my_ftp.py

import os
from pyftpdlib.authorizers import DummyAuthorizer
from pyftpdlib.handlers import FTPHandler
from pyftpdlib.servers import FTPServer

USERNAME = "admin"
PASSWORD = "foobar"

PERMISSION = 'elradfmwMT'

# Read permission
# "e" = change directory (CWD, CDUP commands)
# "l" = list files (LIST, NLST, STAT, MLSD, MLST, SIZE commands)
# "r" = retrieve file from the server (RETR command)

# Write permissions:
# "a" = append data to an existing file (APPE command)
# "d" = delete file or directory (DELE, RMD commands)
# "f" = rename file or directory (RNFR, RNTO commands)
# "m" = create directory (MKD command)
# "w" = store a file to the server (STOR, STOU commands)
# "M" = change file mode / permission (SITE CHMOD command)
# "T" = change file modification time (SITE MFMT command)

PATH = "Documents/Drum Sample" # Change this to your own preference

def main():
    authorizer = DummyAuthorizer()
    shared_dir = os.path.abspath(PATH)

    authorizer.add_user(USERNAME, PASSWORD, shared_dir, perm=PERMISSION)
    authorizer.add_anonymous(shared_dir)

    handler = FTPHandler
    handler.authorizer = authorizer

    handler.passive_ports = range(60000, 65535)
    handler.masquerade_address = 'external'

    # Init FTP server class, listen on 0.0.0.0:2121
    address = ('', 2121)
    server = FTPServer(address, handler)

    server.max_cons, server.max_cons_per_ip = 64, 20
    server.serve_forever()

if __name__ == '__main__':
    main()