OptionaldeadlineAbsolute time by which the socket must open.
OptionalheadersExtra handshake headers; browser WebSockets may reject these.
OptionalmaxMaximum UTF-8 bytes in one signalling JSON message.
OptionalprotocolsWebSocket subprotocol or preference list.
OptionalwebCustom socket constructor for tests or non-browser runtimes.
Connection and handshake options for WebSocket signalling.