22.5.4 The Halt port operation
The halt operation is comparable to the stop operation, but allows entries being already in the queue to be processed with receiving operations

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Examples

myPort.halt;
// No sending allowed on myPort from this moment on; 
//    processing    of    messages    in    the    queue    still    possible.

myPort.receive (mw_myTemplate1);
 // If a message was already in the queue before the halt                                         
//  operation    and    it    matches    mw_myTemplate1,    it    is    processed;                                            //  otherwise    the    receive    operation    blocks