Application written in YouTube video https://bit.ly/2HSPF7n

init.lua

local BLUE_LED = 2

gpio.config({ gpio = BLUE_LED, dir = gpio.IN_OUT })
gpio.write(BLUE_LED, 0)

local api = nil

local function init_api32()
    if api == nil then
        api = require('api32')
            .create({
                auth = {
                    user = 'master',
                    pwd  = 'api32secret'
                }
            })
            .on_post('/led', function(jreq)
                if jreq ~= nil and jreq.State ~= nil then
                    gpio.write(BLUE_LED, jreq.State)
                end

                return {
                    Device = 'Blue LED',
                    State = gpio.read(BLUE_LED)
                }
            end)
    end
end

wifi.mode(wifi.STATION)

wifi.sta.config({
    ssid  = 'Renault 1.9D',
    pwd   = 'renault19',
    auto  = false
})

wifi.sta.on('got_ip', init_api32)

wifi.start()
wifi.sta.connect()

Program.cs

using NApi32;
using System;
using System.Threading;

namespace Api32ClientApp
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.ForegroundColor = ConsoleColor.Green;

            var client = new Api32Client("http://192.168.0.102")
                .Authorize("master", "api32secret");

            var state = true;

            while(true)
            {
                Console.WriteLine("LED goes {0}...",
                    state ? "ON" : "OFF");

                var ledReq = new LedRequest { State = state ? 1 : 0 };
                var ledRes = client.DoPost<LedResponse>("/led", ledReq);

                Thread.Sleep(500); // 0.5 sec
                state = !state; // Invert the state
            }
        }
    }

    // Class for Led Controll Request
    public class LedRequest
    {
        public int State { get; set; }
    }

    // Class for Led Controll Response
    public class LedResponse
    {
        public string Device { get; set; }
        public int State { get; set; }
    }
}