procedure BeginWork(
    AWorkMode: TWorkMode; 
    const ASize: Int64 = 0
); virtual;

BeginWork is a virtual procedure used to trigger the OnBeginWork event. BeginWork maintains the number of reads and writes pending. BeginWork also maintains the size of the initial read and/or write request when the Size is known at the beginning of the request. 

AWorkMode is a TWorkMode enumerated type, and can contain one of the following values: 

ASize is the optional value indicating the number of bytes expected by to be received or sent by the connection. When ASize is omitted, the default value of 0 is assigned. 

Calls to the BeginWork procedure can be nested, but the OnBeginWork event handler will be invoked only for the initial call to BeginWork. 

Applications must assign a procedure to the OnBeginWork event handler in order to respond to the event notification. 

Use EndWork to close the work mode event for the current level. 

Use DoWork to signal when bytes for the current work level are handled. 

When WorkTarget is assigned, work mode events are signalled in the TIdComponent identified by WorkTarget instead of the current object instance.