ESP8266 Remote PC Power Switch (Home Assistant & mDNS) - optocoupler + resistors

#include <ESP8266WiFi.h>
#include <ESP8266WebServer.h>
#include <ESP8266mDNS.h>

/*
 * Project: Wi-Fi PC Remote Power Control & Status Monitor
 * Hardware Components:
 * 1. Controller: NodeMCU ESP8266 V3
 * 2. Isolation: 2x PC817 DIP Optocouplers
 * 3. Resistors: 2x 220 Ohm (1/4W)
 * 4. Power Supply: Micro-USB (5V)
 *
 * Schematic & Wiring Diagram:
 *
 * [ NodeMCU ]                      [ PC817 #1 - Power Control ]             [ Motherboard F_PANEL ]
 *  Pin D1 (GPIO5) ---> [220Ω] ---> Pin 1 (Anode •)
 *  GND --------------------------> Pin 2 (Cathode)
 *                                  Pin 4 (Collector) ----------------------> Pin 7 (POWER SW +)
 *                                  Pin 3 (Emitter) ------------------------> Pin 8 (POWER SW -)
 *
 * [ NodeMCU ]                      [ PC817 #2 - Power LED Sense ]          [ Motherboard F_PANEL ]
 *  Pin D2 (GPIO4) <--------------- Pin 4 (Collector)
 *  GND --------------------------> Pin 3 (Emitter)
 *                                  Pin 2 (Cathode) <----------------------- Pin 3 (PLED -)
 *                                  Pin 1 (Anode •) <------- [220Ω] -------- Pin 1 (PLED +)
 *
 * Hardware Notes:
 * - PC817 Pin 1 is identified by the small indented circle/dot on top of the DIP package.
 * - Pin D2 (GPIO4) uses ESP8266 internal pull-up logic (INPUT_PULLUP).
 * - Target local URL: http://streampc.local
 */

// --- Network Configuration ---
const char* ssid     = "YOUR_WIFI_SSID";
const char* password = "YOUR_WIFI_PASSWORD";

// --- Hostname Configuration ---
const char* hostName = "streampc"; // Resolves to http://streampc.local

// --- Pin Definitions ---
const int PIN_POWER_BTN  = 5; // D1 (GPIO5) -> PC817 #1 (Power Control Output)
const int PIN_POWER_SENS = 4; // D2 (GPIO4) -> PC817 #2 (Power LED Sense Input)

ESP8266WebServer server(80);

// Helper function to pulse power pin
void pressPowerButton(int durationMs) {
  digitalWrite(PIN_POWER_BTN, HIGH);
  delay(durationMs);
  digitalWrite(PIN_POWER_BTN, LOW);
}

// Check power state (Returns true if PC is ON)
bool isPcOn() {
  return digitalRead(PIN_POWER_SENS) == LOW;
}

// Handler for HTML Interface
void handleRoot() {
  String html = "<html><head><meta charset='UTF-8'><meta name='viewport' content='width=device-width, initial-scale=1'><style>body{text-align:center;font-family:Arial,sans-serif;background:#f4f4f4;padding:20px;}h1{display:flex;align-items:center;justify-content:center;margin-bottom:30px;}.indicator{display:inline-block;width:22px;height:22px;border-radius:50%;margin-left:15px;background:#2ecc71;box-shadow: 0 0 10px #2ecc71;transition: 0.3s;}.btn{width:100%;max-width:300px;height:80px;font-size:20px;font-weight:bold;color:white;border:none;border-radius:15px;margin:15px 0;cursor:pointer;display:block;margin-left:auto;margin-right:auto;transition:0.2s;}.btn:active{transform:scale(0.98);}.on{background:#2ecc71;box-shadow:0 5px #27ae60;} .off{background:#e74c3c;box-shadow:0 5px #c0392b;}</style><script>setInterval(function(){  fetch('/status').then(r => r.text()).then(status => {    var ind = document.querySelector('.indicator');    if(status==='ON'){ind.style.background='#2ecc71'; ind.style.boxShadow='0 0 10px #2ecc71';}    else{ind.style.background='#e74c3c'; ind.style.boxShadow='0 0 10px #e74c3c';}  });}, 2000);function safeToggle() {  fetch('/status').then(r => r.text()).then(status => {    if (status === 'ON') { if (confirm('PC is already ON. Power action?')) location.href='/power'; }    else { location.href='/power'; }  });}</script></head><body><h1>PC Remote <span class='indicator'></span></h1><button class='btn on' onclick='safeToggle()'>POWER ON/OFF</button><button class='btn off' onclick=\"if(confirm('FORCE SHUTDOWN (8S)?')){location.href='/force';}\">FORCE SHUTDOWN</button><p>http://streampc.local</p></body></html>";

  server.send(200, "text/html", html);
}

// Endpoint returning plain text status ("ON" or "OFF")
void handleStatus() {
  server.send(200, "text/plain", isPcOn() ? "ON" : "OFF");
}

// Endpoint for standard power tap (500ms)
void handlePower() {
  pressPowerButton(500);
  server.sendHeader("Location", "/");
  server.send(303);
}

// Endpoint for hard shutdown (8000ms / 8s)
void handleForce() {
  pressPowerButton(8000);
  server.sendHeader("Location", "/");
  server.send(303);
}

void setup() {
  Serial.begin(115200);

  // Configure output pin
  pinMode(PIN_POWER_BTN, OUTPUT);
  digitalWrite(PIN_POWER_BTN, LOW);

  // Configure input pin with internal pull-up
  pinMode(PIN_POWER_SENS, INPUT_PULLUP);

  // Static IP Configuration
  IPAddress local_IP(192, 168, 0, 166);
  IPAddress gateway(192, 168, 0, 1);
  IPAddress subnet(255, 255, 255, 0);
  IPAddress primaryDNS(192, 168, 0, 1);

  if (!WiFi.config(local_IP, gateway, subnet, primaryDNS)) {
    Serial.println("STA Failed to configure static IP!");
  }

  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);
  Serial.println("\nConnecting to WiFi...");

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println("\nWiFi Connected!");
  Serial.print("IP Address: ");
  Serial.println(WiFi.localIP());

  // Start mDNS responder for http://streampc.local
  if (MDNS.begin(hostName)) {
    Serial.println("mDNS responder started: http://streampc.local");
  } else {
    Serial.println("Error setting up MDNS responder!");
  }

  // Web server routes
  server.on("/", handleRoot);
  server.on("/status", handleStatus);
  server.on("/power", handlePower);
  server.on("/force", handleForce);

  server.begin();
  Serial.println("HTTP Server started.");
}

void loop() {
  MDNS.update();
  server.handleClient();
}