subscribe method
Implementation
Stream<dynamic> subscribe(String method, [List<dynamic>? params]) {
if (!isWebSocket) {
throw StateError('subscribe requires a WebSocket URL');
}
final payload = jsonEncode({
'jsonrpc': '2.0',
'id': nextId,
'method': method,
'params': params ?? [],
});
// The subscription envelope is formatted; transport must be wired to
// feed incoming notifications into the returned stream.
throw UnimplementedError(
'WebSocket transport not configured -- '
'subscription payload ready: $payload',
);
}