C-C++ Code Example: Retrieving PROPID_Q_MULTICAST_ADDRESS

 

Updated: July 19, 2016

Applies To: Windows 10, Windows 7, Windows 8, Windows 8.1, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, Windows Server 2012 R2, Windows Server Technical Preview, Windows Vista

This example provides an application-defined function that retrieves the PROPID_Q_MULTICAST_ADDRESS property of an existing queue and returns the address to the caller.

This function can return the multicast address associated with a local private queue from information stored on the local computer, but must retrieve information stored in the directory service to return the multicast address associated with a local or remote public queue. This function cannot be used to obtain the multicast address associated with a remote private queue.

A direct format name can be passed to this function only for a local private queue.

For information on how Message Queuing uses multicast addresses to send message to multiple destination queues, see Multiple-Destination Messaging.

To retrieve PROPID_Q_MULTICAST_ADDRESS

  1. Define the maximum number of queue properties to be specified and the queue property counter.

  2. Define the MQQUEUEPROPS structure.

  3. Specify PROPID_Q_MULTICAST_ADDRESS

  4. Initialize the MQQUEUEPROPS structure.

  5. Validate the input parameters provided by the caller.

  6. Call MQGetQueueProperties to retrieve the multicast address associated with the queue. If the call fails the returned error code is returned to the caller.

  7. Pass a pointer to the string containing the retrieved multicast address associated with the queue to the caller on return.

System_CAPS_ICON_note.jpg Note

After your application no longer needs the multicast address buffer, the caller must free the memory allocated for it using MQFreeMemory.

The following code example requires MSMQ 3.0.

HRESULT GetQueueMulticastAddressProp(  
                                     LPCWSTR wszQueueFormatName,   
                                     LPWSTR *pwszValue  
                                     )  
{  
  
  // Define the maximum number of queue properties and a property counter.  
  const int NUMBEROFPROPERTIES = 1;  
  DWORD cPropId=0;  
  
  // Define a queue property structure.  
  MQQUEUEPROPS   QueueProps;  
  QUEUEPROPID    aQueuePropId[NUMBEROFPROPERTIES];  
  MQPROPVARIANT  aQueuePropVar[NUMBEROFPROPERTIES];  
  HRESULT        aQueuePropStatus[NUMBEROFPROPERTIES];  
  HRESULT hr = MQ_OK;  
  
  // Specify the PROPID_Q_MULTICAST_ADDRESS property.  
  aQueuePropId[cPropId] = PROPID_Q_MULTICAST_ADDRESS;  // Property ID  
  aQueuePropVar[cPropId].vt = VT_NULL;                 // Type indicator  
  cPropId++;  
  
  // Initialize the MQQUEUEPROPS structure.  
  QueueProps.cProp = cPropId;  
  QueueProps.aPropID = aQueuePropId;  
  QueueProps.aPropVar = aQueuePropVar;  
  QueueProps.aStatus = aQueuePropStatus;  
  
  // Validate the input string.  
  if (wszQueueFormatName == NULL)  
  {  
    return MQ_ERROR_INVALID_PARAMETER;  
  }  
  
  // Get the queue properties.  
  hr = MQGetQueueProperties(wszQueueFormatName, &QueueProps);  
  if (FAILED(hr))  
  {  
    return hr;  
  }  
  
  // Set the *pwszValue parameter to the pointer to the string containing  
  // the multicast address returned by MQGetQueueProperties.  
  *pwszValue = aQueuePropVar[0].pwszVal;  
  return hr;  
}  

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