- allow to run several copies of program on the same port to use all available CPU cores
- support for cryptography module and use it by default in the docker container
- drop client if it doesn't send a handshake in 10 seconds
- if the handshake was wrong, don't close a connection immediately to prevent active protocol fingerprinting
- use uvloop, high-speed implementation of event loop, if available
- fix binding on port that less than 1024 in docker container