docs: public boolean isClosed()
     {
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.entry(this, tc, "isClosed");
        boolean retValue = false;
  
        if (connectionProxy == null)
        {
           retValue = closed;
        }
        else
        {
           retValue = closed || connectionProxy.isClosed();
        }
  
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(this, tc, "isClosed", ""+retValue);
        return retValue;
     }