Introduction to Bluetooth and J2ME Part 2

In Part 1 we went over the basics of Bluetooth technology and some possible development opportunities Bluetooth gives us. Part 2 of this article goes into a little more detail how to create a Bluetooth server and client. About the Example In keeping things simplistic as possible proper handling of multiple slaves/clients is not implemented essentially it only works with one server and one client. As well the sample is just that sample code, it is coded from the perspective of getting the two nodes to communicate with each without any real effort in "proper" coding technique/design. Remember the focus is to get you started with the actual Java Bluetooth API. Before we continue you should download the JSR 82 Java Doc API from www.bluetooth.org . When you run the program you will notice it outputs Major 512 and Minor 4, according to the chart it is a Phone / Celluar. Server Overview In the server class we need to initialize once again but this time instead of searching for devices we need to setup a server private static String serverUrl = "btspp://localhost:" + BluetoothEchoDemo.RFCOMM_UUID + ";name=rfcommtest;authorize=true"; . . . conn = null; localDevice = LocalDevice.getLocalDevice(); localDevice.setDiscoverable( DiscoveryAgent.GIAC ); notifier = (StreamConnectionNotifier)Connector.open(serverUrl); . . . Now make a connection with the same Generic Connector you use when making HTTP calls. The url definition is as follows: scheme://host:port;parameters Running the Example Download the source and compile from here. You will need to invoke the Sun WTK twice because the outputs are displayed in the consoles. Start one instance and select Server, then start a second instance and select Client (Yes you need to start 2 instances of the WTK not just simply hit the "run" button twice on the same instance because the console of the first instance will not show). Like HTTP calls you may need to answer yes for connections being made. In the end you will see the following in the server console: Starting Echo Server Server Running... Received Message from Client: Say Hello World In the client console you will see: Device Discovered Major Device Class: 512 Minor Device Class: 4 Bluetooth Address: 000060854FBF Bluetooth Friendly Name: WirelessToolkit InquiryCompleted ServicesDiscovered SERVICE_SEARCH_COMPLETED Service URL: btspp://000060854FBF:1;master=false;encrypt=false;authenticate=false Hello Back from Server Summary and What is Missing You should be able to make a basic RFCOMM communication between a Bluetooth client and server. However, even though we went through a lot detail there are still details that were left out or not mentioned. Now that you have a better understanding of Bluetooth with J2ME you need to dive deeper into the following:

An understanding of Service Discovery Database (SDDB)

A more in depth look at UUIDs and other Data Elements

Understand what a Service Record is and what it does

Understanding the relationship between SDDB, Service Record and Data Elements

As a recap the example in this article the primary goal is to give you an introduction to setting up the communication between a master and slave. Rather then jumping into a full example and getting over whelmed this sample code layouts out the bare bones. Along with more research into the APIs and review of more complete samples of Bluetooth you will be on your way to making some exciting new Bluetooth games/aplications. More complete examples are available with developments kits such as: