onTextMessage method
Handles the text message received from the WebSocket server
Implementation
void onTextMessage(String text) async {
final json = jsonDecode(text);
if (json.containsKey(JsonConstants.result)) {
handleServerResponse(json);
} else if (json.containsKey(JsonConstants.error)) {
handleServerError(json);
} else {
handleServerEvent(json);
}
}