A lookup or seed node has the option (using
ENABLE_WEBSOCKET) to enable a WebSocket server on port
WEBSOCKET_PORT (4401 by default). The WebSocket server provides users (e.g., SDK clients) with a subscription-based data querying model as an alternative to polling.
Interacting with the WebSocket server is detailed in our Application Developers section.
The WebSocket server is implemented in libServer in the Zilliqa core, using the WebSocket++ C++ library.