sendMessage method
Send a message to this peer
Implementation
@override
void sendMessage(List<int> message) {
message.insert(0, dataPrefix);
if (open == false) {
throw ShspInstanceException(
'Cannot send message: connection is not open',
instanceId: '${remotePeer.address.address}:${remotePeer.port}',
);
}
_sendMessage(message);
}