MQL5 alerts: Alert, PlaySound and SendNotification

The code

An Expert Advisor that trades nothing: it alerts when a bar closes above or below a level, the previous day's high by default. Turn on the channels you want in its inputs.

Save it as MQL5/Experts/alerts-and-push-notifications.mq5 and compile it in MetaEditor (F7): 0 errors, 0 warnings.

input double InpLevel     = 0.0;         // Price level to watch (0 = previous day's high)
input bool   InpPopup     = true;        // Pop-up alert in the terminal
input bool   InpSound     = false;       // Play a sound
input string InpSoundFile = "alert2.wav"; // Sound file, in the terminal's Sounds folder
input bool   InpPush      = false;       // Push notification to the MetaTrader app on your phone

// Sends one message through every channel that's switched on
void Notify(const string text)
  {
   string msg = StringFormat("%s %s: %s", _Symbol, StringSubstr(EnumToString(_Period), 7), text);
   if(InpPopup)
      Alert(msg);                         // also plays the terminal's alert sound
   if(InpSound && !PlaySound(InpSoundFile))
      PrintFormat("PlaySound(%s) failed: is the file in the Sounds folder?", InpSoundFile);
   if(InpPush)
     {
      // MetaQuotes allows about 2 pushes a second and 10 a minute: keep at least 6 seconds between them
      static ulong lastPush = 0;
      if(lastPush > 0 && GetTickCount64() - lastPush < 6000)
        {
         Print("Push skipped (too soon after the last one): ", msg);
         return;
        }
      ResetLastError();
      if(!SendNotification(StringSubstr(msg, 0, 255)))   // 255 characters at most
         PrintFormat("SendNotification failed: error %d", GetLastError());
      else
         lastPush = GetTickCount64();
     }
  }

int OnInit()
  {
   if(InpPush && (!TerminalInfoInteger(TERMINAL_NOTIFICATIONS_ENABLED) || TerminalInfoInteger(TERMINAL_MQID) == 0))
      Print("Push notifications are off: add your MetaQuotes ID in Tools > Options > Notifications and tick Enable");
   return INIT_SUCCEEDED;
  }

void OnTick()
  {
   static datetime lastBar = 0;
   datetime bar = iTime(_Symbol, PERIOD_CURRENT, 0);
   if(bar == 0 || bar == lastBar)
      return;                             // check once per bar, so one cross sends one message
   lastBar = bar;

   double level = InpLevel > 0.0 ? InpLevel : iHigh(_Symbol, PERIOD_D1, 1);
   double c1    = iClose(_Symbol, PERIOD_CURRENT, 1);
   double c2    = iClose(_Symbol, PERIOD_CURRENT, 2);
   if(level <= 0.0 || c2 <= 0.0)
      return;
   if(c2 <= level && c1 > level)
      Notify(StringFormat("closed above %s at %s", DoubleToString(level, _Digits), DoubleToString(c1, _Digits)));
   else if(c2 >= level && c1 < level)
      Notify(StringFormat("closed below %s at %s", DoubleToString(level, _Digits), DoubleToString(c1, _Digits)));
  }

How it works

• Notify(). One function for every channel, so the signal code doesn't care how the message travels. The symbol and timeframe go first, which matters when several charts alert.
• Alert() shows the message in the terminal's alert window and plays the alert sound set in the terminal's options.
• PlaySound() returns false when the file isn't found. The name is relative to the Sounds folder of the terminal's installation; alert2.wav is one of the files MetaTrader installs.
• The push throttle. MetaQuotes limits push notifications to about 2 a second and 10 a minute. Keeping six seconds between pushes stays under both, and a skipped push is printed rather than lost silently.
• 255 characters. The longest push message accepted; StringSubstr() cuts longer ones.
• The settings check in OnInit(). TERMINAL_NOTIFICATIONS_ENABLED and TERMINAL_MQID tell whether pushes can work at all, so the problem shows at start instead of at the first signal.

Pitfalls

• Alerting on every tick. A condition such as "price is above the level" stays true for hundreds of ticks. Alert on the change (the close crossing the level) and check once per bar.
• Push errors. SendNotification() returns false and GetLastError() says why: 4517 for missing settings (no MetaQuotes ID, or notifications not enabled), 4518 for sending too often, 4516 for an empty message, 4515 when sending failed.
• Testing alerts in the Strategy Tester. The tester doesn't show pop-ups, play sounds or deliver pushes. Test notifications on a demo chart.
• Sound files. PlaySound() plays WAV files from the terminal's Sounds folder; an MP3 or a full path elsewhere doesn't play.

Variations

• Email. SendMail(subject, text) sends through the mail server set in Tools > Options > Email.
• Telegram, Discord or your server. Post the message to a webhook with WebRequest().
• An indicator signal. Replace the level with a cross of two indicator values, read once per bar.
• Mark it too. Draw an arrow where the alert fired with the code in drawing on the chart, so you can review alerts later.
• On TradingView. Pine Script has its own alert functions: alertcondition() vs alert().

Questions

This program is a minimal example written to show one technique, not a trading system, and none of it is a recommendation to trade. Trading involves substantial risk of loss and is not suitable for every investor. Edgoro is a software tool, not a broker or financial adviser: nothing it produces is investment advice, and past or backtested performance does not guarantee future results.