Java and Android mesh/star networking

Question

I'm currently working on an Android project that will need connecting to a Bluetooth device that will dispatch messages to different nodes. This means that I will have to pass the right messages to the appropriate nodes (many micro-controllers).

At the moment, I can send a string or receive a string from the master micro-controller and I think the best way to solve my problem will be that the master micro-controller node simply repeats and broadcasts the message to all the others nodes. For the Android part, I was wondering if it was a good practice to make an array that will contain the id of the receiver and after the data I want to send. The ID will be on 8 bits and the data will be a string. After I will cast the int to a string and concatenate both strings to send my id+data.

Is this a good way to solve my problem or there is a more elegant way to do so?

Answer 1

It would be more efficient to cast the string to bytes and send it all as an array of bytes. Serious network protocols would never use text data like that. If you're just doing a for-fun trial that's ok though.

Here's the real problem I see with your mesh- infinite exponential propagation. Lets say I send a message to someone, and do it by sending it to all of my neighbors. They'll forward it to all their neighbors. Who'll forward it to all their neighbors. Which if there's ever any loop in the graph will cause it to get sent back to someone who's already seen it, who will forward it again. And it will never die. Unless you have no loops, in which case you don't have a mesh and you're very fragile and will likely fragment. You need some way of preventing retransit of the same message- possibly as simple as a message id field and not retransmiting the same message id again. You'd need a large pool of message numbers for that though- something like a 128 bit UUID.