[TOC]

sock-rpc#

• This a Node.js module that implements an RPC server on top wire-protocol from Arma 3 sock.dll extension.

Changelog

• 1.0.8
  • Fix broken typeof2 function
  • Add test case for rawToJSON
• 1.0.7
  • Pull fix for Context from @Fusselwurm
• 1.0.6
  • Fix bug where 1.#QNAN value was not being parsed correctly
• 1.0.5
  • Fix bug where booleans where not being handled when using RAW SQF format
• 1.0.4
  • Add support for requests formatted as Raw SQF (to help with client-side performance)
  • Add support command line arguments --trace-req
• 1.0.3
  • Add support command line arguments --trace-send, and --trace-recv
  • Extend the high level RPC protocol to allow passing "accept" property (supports "application/sqf", and "application/json")
  • Add Client class that can be used to communicate with a remote sock-rpc server
• 1.0.1 - Major version bump due to design changes in callback mechanism
  • Added SEVERE level logging to show the the actual JSON string when parsing error happens
• 1.0.0 - Major version bump due to design changes in callback mechanism
  • Improved logging using the util-logging module
  • Improved command line processing using yargs module
  • Design change: callback passed into registered RPC functions are now always the last argument
  • Design change: callback passed into registered RPC functions have now the following signature: callback(err, result)
• 0.0.2 - Update to add license file
• 0.0.1 - Initial release

Prerequisites

• Download and install Node.js

Installation

• From the head of the master branch
  .

npm install -g git+https://bitbucket.org/micovery/sock-rpc.git

.

• From the npmjs.org repository
  .

npm install -g sock-rpc  

.

How to use

Create a Node.js JavaScript file (e.g. example.js) containing the functions to be used by the RPC server.

"use strict";
 
var rpc = require('sock-rpc');
 
/**
 *  Echo back all arguments passed.
 *  echo(...,callback);
 */
rpc.register("echo", function () {
  var args = Array.prototype.slice.call(arguments, 0);
  var callback = args.pop();
  callback(null, args);
});
 
/**
 *  Get date (no arguments)
 */
rpc.register("getDate", function (callback) {
  callback(null, new Date().toString());
});
rpc.listen();

.
All registered method's must use the callback mechanism to pass the result to the client, and by doing so indicate that the execution is complete.
If a method does not invoke the callback, the client side will likely hang while it waits for a response from the server.
.
In order to indicate that an error has happened, you can pass an error as the first argument to the callback.
.

 
  callback(new Error("Cannot compute!"));
 

Starting the Server

The following commands shows how to start the RPC server on port 1337, and IPv6 loolback address ::1 using the Windows command-line.

set NODE_PATH=%AppData%\npm\node_modules

node example.js -port=1337 -host=::1

.

API

• listen([host], [port])

  • host (type: string, optional) - Host name, or address to listen on

    If not provided, it defaults to command line argument -host=
    If -host is not provided, it defaults to localhost
    .

  • port (type: number, optional) - Port number to listen on

    If not provided, it defaults to command line argument -port=
    If -port is not provided, it defaults to a random available port
    .

• register(functions)

  • functions (type: object, required) - An object containing functions
    .

• register(name, function)

  • name (type: string, required) - Host name, or address to listen on

  • function (type: function, required) - Function to register
    .

Low-Level Protocol

At the lowest level, this module uses the SOCK-TCP wire-protocol from the sock.dll Arma 3 extension, acting as the server. .

//First, wait for client to send a request message
server: recv: request-header-foo (4 bytes, unsigned long, network byte order, length of the body that follows)
server: recv: request-body-foo (variable bytes, actual request message data)

//then send the response message
server: send: response-header-foo (4 bytes, unsigned long, network byte order, length of the body that follows)
server: send: response-body-foo (variable bytes, actual response message data)

.

That's pretty much it, server receives a request message, and replies with a response message.
.

• The server does not guarantee that response messages are sent to client matching the same order as the request messages.
• The client must either send only one request message at a time, and wait for the response ... or keep track of of the messages using sequence IDs.
• In Arma 3, the execution of extensions is single threaded. This guarantees that only one request packet is sent at a time.
• Client may send a zero-length request message. The server must ignore zero-length messages and continue on processing.

High-Level Protocol

At a high level, this module uses a protocol similar to JSON-RPC, for client requests.
For server responses, on the other hand, they are formatted as SQF code that can be compiled dynamically inside the game.

.

    //First wait for client to send a JSON-RPC request
    server: recv: {"method":"methodName", "params": ["param1", "param2"],...]}

    //then send the SQF response
    server: send: [false,"response"]

.

The response to a client request is always an SQF array with two elements.

   [error-state, mapped-response-data]

.

• error-state (type: boolean) - This is an indicator of whether or not an error occurred while processing the request.

  • tue - if an error occurred processing the client's request
  • false - if no error occurred processing the client's request
    .

• mapped-response-data

  • The mapped-response-data, as the name indicates, is simply the output of the RPC invocation mapped into its equivalent SQF representation.
  • When an error occurs (error-state is true), then mapped-response-data is an SQF string containing explanation of the error.
  • If no error occurs, then the mapped-response-data can be of any SQF data type.
    .