subEvents method
void
subEvents()
Subscribe to open, close and packet events
@api private
Implementation
void subEvents() {
if (subs!.isNotEmpty == true) return;
Manager io = this.io;
subs = [
util.on(io, 'open', onopen),
util.on(io, 'packet', onpacket),
util.on(io, 'close', onclose)
];
}