How to get a simple and crude dubbo calling module

dubbo calling module core function is to initiate a remote method invocation and return smoothly to get a result, its architecture is composed as follows:
1. Transparent Proxy: through dynamic agent technology, shielded remote call details to improve programming friendliness.
2. Load Balancing: When there are multiple providers is how to choose which load algorithm calls.
3. Fault Tolerance: strategy when a service call fails to take
4. Call: support synchronous calls, asynchronous calls
5. get results: refers to the synchronous wait for the results returned, or an asynchronous callback notification to obtain results.