Socket Programming syntax not recognize

 
I'm try to exchange data using socket. I try to follow the example from this documentation https://www.mql5.com/en/docs/network/socketconnect, but socket command are not recognized by MQL. Is there any include or something that I missed?
Documentation on MQL5: Network Functions / SocketConnect
Documentation on MQL5: Network Functions / SocketConnect
  • www.mql5.com
//|                                                SocketExample.mq5 | //|                        Copyright 2018, MetaQuotes Software Corp. | //|                                             https://www.mql5.com | "Add Address to the list of allowed ones in the terminal settings to let the example work...
 
That's mql5 functions. Not mql4.