How HDFs works in Java

1.RPC
1.1 RPC (Remote Procedure Call) remoting procedure calls.
The remote procedure refers to the same process.
1.2 RPC has a minimum of two procedures. Caller (client), callee (server).
The 1.3 client initiates the request, invokes the method in the specified IP and port server, and returns the result of the call to the client.
1.4 RPC is the foundation of Hadoop construction.

2. What is the understanding gained through examples?
2.1 RPC is a remote procedure call.
2.2 The client invokes the service-side method, which means invoking the method in the server-side object.
2.3 If the server object allows the client to invoke, then this object must implement the interface.
2.4 If a client can invoke a method on a server-side object, these methods must be in the interface of the object.

How HDFs works in Java