Remote Procedure Call

Related page: https://github.com/lcnvdl/gms2-networking/blob/main/docs/RPC.md

1. Definition

In distributed computing, a remote procedure call (RPC) is when a computer program causes a procedure (subroutine) to execute in a different address space (commonly on another computer on a shared network), which is coded as if it were a normal (local) procedure call, without the programmer explicitly coding the details for the remote interaction.

2. RPC in Auto-magic Networking System

The main idea is to allow Senders and Receivers to call functions almost as easily as if they were called within the same instance.

3. Registering RPC

When the application is being loaded, you must prepare the ground for RPC. The first step you have to do is register the functions.

3.1. Simple function register

CREATE EVENT

nw_rpc_register("my_function", function(myArgs) {
    return myArgs.a + myArgs.b; 
});

3.2. Security

You can add some security settings, in order to prevent the bad usage of the RPC.

Complete example (with all 4 variations)

CREATE EVENT

nw_rpc_register("rpc_fn", function(myArgs) {   
    show_debug_message("RPC works!"); 
});
 
nw_rpc_register("broadcast_fn", function(myArgs) {
    show_debug_message("Broadcast works!"); 
});
 
nw_rpc_register("multiply", function(myArgs) {   
    return myArgs.a * myArgs.b; 
});  
 
nw_rpc_register("check_on_sender", function(myArgs) { 
    return "Sender is OK"; 
});  
 
//  Allows calling or broadcasting 
nw_rpc_set_security("rpc_fn", { from: "sender", to: "1-*" });  
 
//  Allows calling only by broadcasting 
nw_rpc_set_security("add", { from: "sender", to: "*" });  
 
//  Allows only calling by rpc 
nw_rpc_set_security("multiply", { from: "sender", to: "1" });  
 
//  Allows calling from Receiver to Sender 
nw_rpc_set_security("multiply", { from: "receiver" });
 

4. Interactions

4.1. Rpc Call - Sender (client) calls to Receiver (server)

The Sender is on client-side. The Receiver is on server-side (and it's replicated on the rest of clients).

The Sender calls to the Server-side Receiver's function, in order to receive an answer.

Diagram code

How to call it?

In the Sender, you must call:

nw_rpc_sender_call("my_function", myArgs, myCallback);

The callback will run once the Sender receives the answer from the Receiver. The function will fail if the sender is not running on client-side.

4.2. Rpc Call - Receiver (client or server) calls to Sender (server or client)

The Receiver calls to the Senders's function, in order to receive an answer.

Diagram code

How to call it?

In the Receiver, you must call:

nw_rpc_receiver_call("my_function", myArgs, myCallback);

The callback will run once the Receiver receives the answer from the Sender.

4.3. Rpc Call - Sender (client or server) broadcasts to Receivers (server or client)

The Sender broadcasts calling each Receiver's function. It won't expect an answer, but an ACK.

Diagram code

How to call it?

In the Sender, you must call:

nw_rpc_sender_broadcast("my_function", myArgs, myCallback);

The callback will run once the Sender receives all ACK signals.

4.4. Rpc Call - Self-call

The entity calls its own Rpc Function.

How to call it?

nw_rpc_self_call("my_function", myArgs, myCallback);