This is a simple tcp server with PoW DDOS protection. It is a simple server that listens for incoming connections and checks if the client has done a PoW before accepting the connection.

I was comparing Hashcash to Guided_tour_puzzle_protocol

I choose Hashcash becasue of the simplicity both in implementing and understanding, Guided tour puzzle protocol involves a lot of rounds of rpc calls.

For building docker images: make dockerbuild make dockerbuildclient

1. It can be used just as go binaries. Server: go run ./cmd/server/main.go Client: go run ./cmd/client/main.go localhost:8080
2. Can be used as docker containers. After you have docker images: docker-compose up - will start both server and client, you can find the quote in client logs. docker compose run client - will restart the client

1. I didn't have time to cover the code with unit tests. I would like to add tests for the server and the PoW algorithm.
2. For distributed environment in-memory cache can be replaced with Redis.
3. A lot of parameters are hardcoded. It would be nice to move them to the configuration file.