We have a fully-working java program which can connect to another computer and can send messages from this(both sides run java and we used SPP Server and Client), however when trying to connect to the NXT Brick and send a message via Bluetooth we are able to pair with the brick and we can send a message but we have no idea if the NXT receives it.
When we tried to use Java SPPClient on the computer(we provide the ServerURL of NXT to java program) to send the message to NXT Brick running the RobotC, it doesn't work. On java side, the error is given:
Failed to connect;  A socket operation failed because the destination host was down.
Is the error we receive on Java.
Using RobotC the brick is waiting for a message to be sent and it is awaiting 3 integers to help the robot move.