command-io-test.php

<?php
echo file_get_contents("command.txt");
?>

Invalid Get.ino

#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>

// Network
const char *ssid = "Your SSID Here";
const char *pswd = "Your Password Here";
const char *commandIOPath = "http://withoutssl.yutokun.com/ac-switcher/command-io-test.php";

void setup()
{
  pinMode(LED_BUILTIN, OUTPUT);
  Serial.begin(115200, SERIAL_8N1);
  while (!Serial)
    delay(50);

  ConnectToWiFi();

  digitalWrite(LED_BUILTIN, HIGH);
}

void ConnectToWiFi()
{
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, pswd);
  Serial.println();
  Serial.println("Connecting to Wi-Fi...");
  while (WiFi.status() != WL_CONNECTED)
  {
    Serial.print(".");
    delay(1000);
  }

  Serial.println("Connected.");

  Serial.print("IP Address: ");
  Serial.println(WiFi.localIP());
}

void loop()
{
  String command = GET(commandIOPath);
  Serial.println();
  Serial.println("Received: " + command);

  for (size_t i = 0; i < 3; i++)
    delay(1000);
}

String GET(const char *host)
{
  HTTPClient http;
  http.begin(host);
  int httpCode = http.GET();

  String result = "";
  if (httpCode < 0)
  {
    result = http.errorToString(httpCode);
  }
  else if (http.getSize() < 0)
  {
    result = "size is invalid";
  }
  else
  {
    result = http.getString();
  }

  http.end();
  return result;
}