CtYun is a .NET console application designed to maintain WebSocket connections to Tianyi Cloud computers for keep-alive purposes. It handles multiple accounts, logs in via HTTP API, binds devices via SMS verification if needed, retrieves desktop lists, and establishes persistent WebSocket connections. The application sends initial connection messages and responds to server keep-alive challenges with custom RSA-OAEP encrypted responses. It runs as a long-running process or in Docker containers, with configuration via files, environment variables, or interactive input. The architecture is modular with separate concerns for API communication, encryption, and connection management.