FMWebSocketManager is focusing on purely byte stream for the best performance, which json style events are excluded unfortunately. We prefer using "label ID" style for identify different data type. In theory, you may create your own data structure for it. For example, create your own encoder/decoder for "events(with data) in json string -> metadata bytes for identify your data structure + json data byte". We might consider adding this feature into our To-Do list, but probably not in high priority at the moment.