Forex MT4 platform - what type of protocol(s)/technology is used to update the charts in real-time?
soap/restful web service?
The data is updated in real-time,
( 2 months ago )
A lot of indeed smart man*years has been burnt on reverse-engineered efforts to tap into MT4/Server <--> MT4/Terminal C/S communication.
Some have died by themselves.
Some have failed to survive the next change introduced by just another Build XYZ.
Some have even made their way up to the court suits from MetaQuotes, Inc., for violation or infringements of the rights to protect one´s intellectual property.
So, one shall rather really know, what is going to follow.
How it works?
Recent MT4/Terminal Build 670+ uses several regular streaming connections to MT4/Server
It does not take much time or efforts to employ a port-scanner of whatever brand to map, decode and analyse further internals. Nevertheless, do not rather forget the warning, [Initial note] rulez.
There are no direct ways to "update" OHLC-candle / Volume objects of the MT4/Terminalgraph
There are many ways to add and control additional visual objects into the MT4 graphs, incl. but not limited to, compose a fully-fledged new, layered, augmented GUI, where user-defined <application-code> retains the full real-time control of both the MVC-GUI-elements and the TradingExecutionEngine.
Can a current Metatrader proprietary architecture get extended?
Historically some three principal epochs / approaches were used.
3rd party DLL based communications
Windows O/S services based communications
MetaQuotes, Inc., "new"-MQL4 ( post Build 600+ ) language extensions for socket communications
User-defined <application-code> can safely deploy rather a thread-safe external messaging infrastructure, to better "escape" from a (fragile, namely in post Build 670+ epoch) MT4 internalities and retain a full control over the "own" messaging / streaming layer.
MT4/Terminal with socket/remote python-based CLI terminal & add-on pseudo-language for both trading and scripted test-case batteries´ automated runs
MT4/Terminal with socket/remote external integrated RSS-feed service
MT4/Terminal with socket/remote GPU-hosted numerical solver for AI/ML decision making
MT4/Terminal with socket/remote cloud-based peer-to-peer community messaging