RTI Connext C API  Version 6.1.1
Request-Reply Examples

Examples on how to use the request-reply API. More...

Examples on how to use the request-reply API.

Request-Reply code examples.

Request-Reply Examples

DDS Types

RTI Connext uses DDS data types for sending and receiving requests and replies. Valid types are those generated by the rtiddsgen code generator, the DDS built-in types, and DynamicData. Refer to the User's Manual and the following links for more information:

Set up

Requester: sending requests and receiving replies

Replier: receiving requests and sending replies

The examples in this section require the following header files:

#include "connext_c/connext_c_requester.h"
#include "connext_c/connext_c_replier.h"
#include "connext_c/connext_c_simple_replier.h"

Creating a Requester

Creating a Requester with optional parameters

Requester example

Taking loaned samples

Correlating requests and replies

Creating a Replier

Replier example

SimpleReplier example

Configuring Request-Reply QoS profiles

If you do not specify your own quality of service parameters (in RTI_Connext_RequesterParams and RTI_Connext_ReplierParams), a FooBarRequester and FooBarReplier are created using a default configuration. That configuration is equivalent to the one in the following QoS profile called "default":

<?xml version="1.0"?>
<dds xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="../../../resource/schema/rti_dds_qos_profiles.xsd">
<qos_library name="RequestReplyExampleProfiles">
<!-- Default QoS:
This profile contains the QoS that Requesters and Repliers
would use by default. We can use it as a base profile to inherit
from and override some parameters
-->
<qos_profile name="default">
<datawriter_qos>
<!-- Strict reliable -->
<reliability>
<kind>RELIABLE_RELIABILITY_QOS</kind>
<max_blocking_time>
<sec>10</sec>
<nanosec>0</nanosec>
</max_blocking_time>
</reliability>
<history>
<kind>KEEP_ALL_HISTORY_QOS</kind>
</history>
<!-- These are typical protocol parameters for a reliable
DataWriter -->
<protocol>
<rtps_reliable_writer>
<max_heartbeat_retries>
LENGTH_UNLIMITED
</max_heartbeat_retries>
<heartbeats_per_max_samples>
2
</heartbeats_per_max_samples>
<heartbeat_period>
<sec>0</sec>
<nanosec>100000000</nanosec> <!--100ms -->
</heartbeat_period>
<fast_heartbeat_period>
<sec>0</sec>
<nanosec>10000000</nanosec> <!--10ms -->
</fast_heartbeat_period>
<late_joiner_heartbeat_period>
<sec>0</sec>
<nanosec>10000000</nanosec> <!--10ms -->
</late_joiner_heartbeat_period>
<max_nack_response_delay>
<sec>0</sec>
<nanosec>0</nanosec>
</max_nack_response_delay>
<min_nack_response_delay>
<sec>0</sec>
<nanosec>0</nanosec>
</min_nack_response_delay>
<max_send_window_size>32</max_send_window_size>
<min_send_window_size>32</min_send_window_size>
</rtps_reliable_writer>
</protocol>
<writer_resource_limits>
<!-- This setting enables efficient communication
between a replier and an arbitrary number of requesters
-->
<max_remote_reader_filters>
LENGTH_UNLIMITED
</max_remote_reader_filters>
</writer_resource_limits>
</datawriter_qos>
<datareader_qos>
<!-- Strict reliable -->
<reliability>
<kind>RELIABLE_RELIABILITY_QOS</kind>
<max_blocking_time>
<sec>10</sec>
<nanosec>0</nanosec>
</max_blocking_time>
</reliability>
<history>
<kind>KEEP_ALL_HISTORY_QOS</kind>
</history>
<!-- These are typical protocol parameters for a reliable
DataReader -->
<protocol>
<rtps_reliable_reader>
<max_heartbeat_response_delay>
<sec>0</sec>
<nanosec>0</nanosec>
</max_heartbeat_response_delay>
<min_heartbeat_response_delay>
<sec>0</sec>
<nanosec>0</nanosec>
</min_heartbeat_response_delay>
</rtps_reliable_reader>
</protocol>
</datareader_qos>
</qos_profile>
<!-- This is the profile used by the Requester.
It inherits from "default", defined above,
and overrides some QoS -->
<qos_profile name="RequesterExampleProfile"
base_name="default">
<!-- QoS for the data writer that sends requests -->
<datawriter_qos>
<durability>
<kind>TRANSIENT_LOCAL_DURABILITY_QOS</kind>
</durability>
</datawriter_qos>
<!-- QoS for the data reader that receives replies -->
<datareader_qos>
<durability>
<kind>VOLATILE_DURABILITY_QOS</kind>
</durability>
</datareader_qos>
</qos_profile>
<!-- This is the profile used by the Replier.
It inherits from "default", defined above,
and overrides some QoS -->
<qos_profile name="ReplierExampleProfile"
base_name="default">
<!-- QoS for the data writer that sends replies -->
<datawriter_qos>
<durability>
<kind>VOLATILE_DURABILITY_QOS</kind>
</durability>
</datawriter_qos>
<!-- QoS for the data reader that receives requests -->
<datareader_qos>
<durability>
<kind>TRANSIENT_LOCAL_DURABILITY_QOS</kind>
</durability>
</datareader_qos>
</qos_profile>
</qos_library>
</dds>

You can use the profile called "RequesterExampleProfile", which modifies some parameters from the default. The example Creating a Requester with optional parameters shows how to create a FooBarRequester using this profile.

See also
Creating a Requester with optional parameters
Configuring QoS Profiles with XML