1. Echo Example¶
The following YAML configuration file configures a DDS Router to create a
Simple Participant in Domain Id 0
and an
Echo Participant that will print in stdout
every message get in Domain 0
,
as well as information regarding discovery events.
##################################
# CONFIGURATION VERSION
version: v5.0 # 0
##################################
# ALLOWED TOPICS
# Allowing FastDDS and ROS2 HelloWorld demo examples topics
allowlist:
- name: HelloWorldTopic # 1
type: HelloWorld # 1
- name: rt/chatter # 2
type: std_msgs::msg::dds_::String_
##################################
# PARTICIPANTS
participants:
##################################
# SIMPLE PARTICIPANT
# This participant will subscribe to topics in allowlist in specific domain and listen every message published there
- name: SimpleParticipant # 3
kind: local # 4
domain: 0 # 5
##################################
# ECHO PARTICIPANT
# This Participant will print in stdout every message received by the other Participants, as well as discovery information
- name: EchoParticipant # 6
kind: echo # 7
discovery: true # 8
data: true # 9
verbose: true # 10
1.1. Configuration¶
1.1.1. Allowed Topics¶
This section lists the Topics that the DDS Router will route from
one Participant to the other.
Topic HelloWorldTopic
with datatype HelloWorld
,
and ROS 2 topic rt/chatter
with datatype std_msgs::msg::dds_::String_
will be forwarded from
SimpleParticipant
to EchoParticipant
, that will print the message in stdout
.
allowlist:
- name: HelloWorldTopic # 1
type: HelloWorld # 1
- name: rt/chatter # 2
type: std_msgs::msg::dds_::String_
1.1.2. Simple Participant¶
This Participant is configured with a name, a kind and the Domain Id, which is 0
in this case.
- name: SimpleParticipant # 3
kind: local # 4
domain: 0 # 5
1.1.3. Echo Participant¶
This Participant is configured to display information regarding messages received, as well as discovery events. See Echo Participant Configuration for more details.
- name: EchoParticipant # 6
kind: echo # 7
discovery: true # 8
data: true # 9
verbose: true # 10
1.2. Execute example¶
For a detailed explanation on how to execute the DDS Router, refer to this section.
Note
Internal entities for a specific topic are only created once a data receiver (Reader/Subscriber) is discovered.
Hence, for these example to work, either substitute allowlist
for builtin-topics in the
configuration file, or launch a subscriber/listener in the same domain (0
).
1.2.1. Execute with Fast DDS HelloWorld Example¶
Execute a Fast DDS HelloWorld example:
./DDSHelloWorldExample publisher
Execute DDS Router with this configuration file (available in
<path/to/ddsrouter_tool>/share/resources/configurations/examples/echo.yaml
).
The expected output from the DDS Router, printed by the Echo Participant
is:
New endpoint discovered: Endpoint{01.0f.b8.d9.81.30.3d.a7.01.00.00.00|0.0.1.3;writer;DdsTopic{HelloWorldTopic;HelloWorld;Fuzzy{Level(20) TopicQoS{TRANSIENT_LOCAL;RELIABLE;SHARED;depth(5000)}}};SpecificEndpointQoS{Partitions{};OwnershipStrength{0}};Active;ParticipantId{SimpleParticipant}}.
In Endpoint: 01.0f.b8.d9.81.30.3d.a7.01.00.00.00|0.0.1.3 from Participant: ParticipantId{SimpleParticipant} in topic: DdsTopic{HelloWorldTopic;HelloWorld;Fuzzy{Level(20) TopicQoS{VOLATILE;BEST_EFFORT;SHARED;depth(5000)}}} payload received: Payload{00 01 00 00 01 00 00 00 0b 00 00 00 48 65 6c 6c 6f 57 6f 72 6c 64 00 00} with specific qos: SpecificEndpointQoS{Partitions{};OwnershipStrength{0}}.
In Endpoint: 01.0f.b8.d9.81.30.3d.a7.01.00.00.00|0.0.1.3 from Participant: ParticipantId{SimpleParticipant} in topic: DdsTopic{HelloWorldTopic;HelloWorld;Fuzzy{Level(20) TopicQoS{VOLATILE;BEST_EFFORT;SHARED;depth(5000)}}} payload received: Payload{00 01 00 00 02 00 00 00 0b 00 00 00 48 65 6c 6c 6f 57 6f 72 6c 64 00 00} with specific qos: SpecificEndpointQoS{Partitions{};OwnershipStrength{0}}.
...
In Endpoint: 01.0f.b8.d9.81.30.3d.a7.01.00.00.00|0.0.1.3 from Participant: ParticipantId{SimpleParticipant} in topic: DdsTopic{HelloWorldTopic;HelloWorld;Fuzzy{Level(20) TopicQoS{VOLATILE;BEST_EFFORT;SHARED;depth(5000)}}} payload received: Payload{00 01 00 00 0a 00 00 00 0b 00 00 00 48 65 6c 6c 6f 57 6f 72 6c 64 00 00} with specific qos: SpecificEndpointQoS{Partitions{};OwnershipStrength{0}}.
1.2.2. Execute with ROS 2 demo nodes¶
Execute a ROS 2 demo_nodes_cpp
talker in default domain 0
:
ros2 run demo_nodes_cpp talker
Execute DDS Router with this configuration file (available in
<path/to/ddsrouter_tool>/share/resources/configurations/examples/echo.yaml
).
The expected output from the DDS Router, printed by the Echo Participant
is:
New endpoint discovered: Endpoint{01.0f.b8.d9.b6.3a.7d.95.01.00.00.00|0.0.1.3;writer;DdsTopic{ros_discovery_info;rmw_dds_common::msg::dds_::ParticipantEntitiesInfo_;Fuzzy{Level(20) TopicQoS{TRANSIENT_LOCAL;RELIABLE;SHARED;depth(5000)}}};SpecificEndpointQoS{Partitions{};OwnershipStrength{0}};Active;ParticipantId{SimpleParticipant}}.
New endpoint discovered: Endpoint{01.0f.b8.d9.b6.3a.7d.95.01.00.00.00|0.0.2.4;reader;DdsTopic{ros_discovery_info;rmw_dds_common::msg::dds_::ParticipantEntitiesInfo_;Fuzzy{Level(20) TopicQoS{TRANSIENT_LOCAL;RELIABLE;SHARED;depth(5000)}}};SpecificEndpointQoS{Partitions{};OwnershipStrength{0}};Active;ParticipantId{SimpleParticipant}}.
...
New endpoint discovered: Endpoint{01.0f.b8.d9.b6.3a.7d.95.01.00.00.00|0.0.12.3;writer;DdsTopic{rt/chatter;std_msgs::msg::dds_::String_;Fuzzy{Level(20) TopicQoS{VOLATILE;RELIABLE;SHARED;depth(5000)}}};SpecificEndpointQoS{Partitions{};OwnershipStrength{0}};Active;ParticipantId{SimpleParticipant}}.
In Endpoint: 01.0f.b8.d9.b6.3a.7d.95.01.00.00.00|0.0.12.3 from Participant: ParticipantId{SimpleParticipant} in topic: DdsTopic{rt/chatter;std_msgs::msg::dds_::String_;Fuzzy{Level(0) TopicQoS{VOLATILE;BEST_EFFORT;SHARED;depth(1000)}}} payload received: Payload{00 01 00 00 0f 00 00 00 48 65 6c 6c 6f 20 57 6f 72 6c 64 3a 20 31 00 00} with specific qos: SpecificEndpointQoS{Partitions{};OwnershipStrength{0}}.
In Endpoint: 01.0f.b8.d9.b6.3a.7d.95.01.00.00.00|0.0.12.3 from Participant: ParticipantId{SimpleParticipant} in topic: DdsTopic{rt/chatter;std_msgs::msg::dds_::String_;Fuzzy{Level(0) TopicQoS{VOLATILE;BEST_EFFORT;SHARED;depth(1000)}}} payload received: Payload{00 01 00 00 0f 00 00 00 48 65 6c 6c 6f 20 57 6f 72 6c 64 3a 20 32 00 00} with specific qos: SpecificEndpointQoS{Partitions{};OwnershipStrength{0}}.
...