Demo six: RPC

Now what if we need to run a function on a remote computer and wait for the result? For that we going to use Remote Procedure Call or RPC.
Our RPC will work like this:
- When the Client starts up, it creates an anonymous exclusive callback queue.
- For an RPC request, the Client sends a message with two properties: reply_to, which is set to the callback queue and correlation_id, which is set to a unique value for every request.
- The request is sent to an rpc_queue queue.
- The RPC worker (aka: server) is waiting for requests on that queue. When a request appears, it does the job and sends a message with the result back to the Client, using the queue from the reply_to field.
- The client waits for data on the callback queue. When a message appears, it checks the correlation_id property. If it matches the value from the request it returns the response to the application.

Running Locally

First we need to start server by running following command,
```
node server.js
```
Now request fibonacci number from client,
```
node client.js 30
```