At the end of your sendHubCommand you are missing one final important parameter, the IP and Port in Hex. So after …LAN, HexIP:HexPort))
At least that worked for me a long time ago. Thus is the old post that helped me:
Edit: search the community for the Java toHexString method that can help you convert the IP. Here is an example from one SmartApp. Remember both IP and Port need to be in Hex.
private String convertIPToHex(ipAddress) {
return Long.toHexString(convertIntToLong(ipAddress));
}