You are here: Part 2: Core Concepts > Sending Data > DataWriter QosPolicies > TRANSPORT_SELECTION QosPolicy (DDS Extension)


The TRANSPORT_SELECTION QosPolicy allows you to select the transports that have been installed with the DomainParticipant to be used by the DataWriter or DataReader.

An application may be simultaneously connected to many different physical transports, e.g., Ethernet, Infiniband, shared memory, VME backplane, and wireless. By default, the middleware will use up to 4 transports to deliver data from a DataWriter to a DataReader.

This QosPolicy can be used to both limit and control which of the application’s available transports may be used by a DataWriter to send data or by a DataReader to receive data.

It includes the member in . For more information, please refer to the API Reference HTML documentation.



Field Name




A sequence of aliases for the transports that may be used by the DataWriter or DataReader.

Connext DDS allows you to configure the transports that it uses to send and receive messages. A number of built-in transports, such as UDPv4 and shared memory, are available as well as custom ones that you may implement and install. Each transport will be installed in the DomainParticipant with one or more aliases.

To enable a DataWriter or DataReader to use a particular transport, add the alias to the enabled_transports sequence of this QosPolicy. An empty sequence is a special case, and indicates that all transports installed in the DomainParticipant can be used by the DataWriter or DataReader.

For more information on configuring and installing transports, please see the API Reference HTML documentation (from the Modules page, select RTI DDS API Reference, Pluggable Transports).


Suppose a DomainParticipant has both UDPv4 and shared memory transports installed. If you want a particular DataWriter to publish its data only over shared memory, then you should use this QosPolicy to specify that restriction.


This QosPolicy cannot be modified after the Entity is created.

It can be set differently for the DataWriter and the DataReader.

Related QosPolicies

Applicable Entities

System Resource Considerations

By restricting DataWriters from sending or DataReaders from receiving over certain transports, you may decrease the load on those transports.

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