❗️ In the browser sandbox, tcp connections cannot be reset — repeated tests may bias the results. It is recommended to use a separate incognito mode or manually reset the connection for each test (e.g., in Chrome at chrome://net-internals/#sockets).

💡 DPI (method tcp 16-20) and host alive checker / See here for more details.
This checker (and others) are available in this open-source repository.