Handling MetaTrader 5 Depth of Market Events
Summary
This article explains how an MQL5 expert advisor can subscribe to Depth of Market updates, retrieve the current book, and process its price, volume, and side fields. The event handler receives the symbol whose book changed; initialization subscribes to book events, and deinitialization releases the subscription. A sample workflow filters for the chart symbol, obtains the book array, and logs its entries.
The article also describes a simple display panel that refreshes whenever a book event arrives, illustrating how the same data can feed a user interface. Its evidence is a terminal log from a futures instrument, showing sell and buy entries with associated prices and volumes. The author notes that event broadcasting behavior differed across terminal builds and reports observing updates only for the assigned symbol in the build used. Book depth depends on the broker, and the article teaches event handling and data access rather than a trading signal or profitable strategy.
Key ideas
- Subscribe to Depth of Market events before processing them, then release the subscription during deinitialization.
- The event handler identifies the symbol whose order book changed.
- Retrieve book records as an array containing order side, price, and volume, and filter for the intended symbol.
- A panel or other interface can refresh its display whenever a book update arrives.
- Book contents and event behavior can depend on broker data and terminal version.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.