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
.
##################################
# ALLOWED TOPICS
# Allowing FastDDS and ROS2 HelloWorld demo examples topics
allowlist:
[
{name: "HelloWorldTopic", type: "HelloWorld"}, # 1
{name: "rt/chatter", type: "std_msgs::msg::dds_::String_"}, # 2
]
##################################
# SIMPLE PARTICIPANT
# This participant will subscribe to topics in allowlist in specific domain and listen every message published there
SimpleParticipant: # 3
type: local # 4
domain: 0 # 5
##################################
# ECHO PARTICIPANT
# This Participant will print in stdout every message received by the other Participants
EchoParticipant: # 6
type: echo # 7
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", type: "HelloWorld"}, # 1
{name: "rt/chatter", type: "std_msgs::msg::dds_::String_"}, # 2
]
1.1.2. Simple Participant¶
This Participant is configured with a name, a type and the Domain Id, which is 0
in this case.
SimpleParticipant: # 3
type: local # 4
domain: 0 # 5
1.1.3. Echo Participant¶
This Participant does not require further configuration than name and type.
EchoParticipant: # 6
type: echo # 7
1.2. Execute example¶
For a detailed explanation on how to execute the DDS Router, refer to this section.
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>/src/ddsrouter/resources/configurations/examples/echo.yaml
).
The expected output from the DDS Router, printed by the Echo Participant
is:
Echo Participant: ParticipantId{EchoParticipant} has received from Endpoint: 01.0f.44.59.e6.de.2a.c8.01.00.00.00|0.0.1.3 in topic: Topic{HelloWorldTopic, HelloWorld} the following payload: <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}>
Echo Participant: ParticipantId{EchoParticipant} has received from Endpoint: 01.0f.44.59.e6.de.2a.c8.01.00.00.00|0.0.1.3 in topic: Topic{HelloWorldTopic, HelloWorld} the following payload: <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}>
...
Echo Participant: ParticipantId{EchoParticipant} has received from Endpoint: 01.0f.44.59.e6.de.2a.c8.01.00.00.00|0.0.1.3 in topic: Topic{HelloWorldTopic, HelloWorld} the following payload: <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}>
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>/src/ddsrouter/resources/configurations/examples/echo.yaml
).
The expected output from the DDS Router, printed by the Echo Participant
is:
Echo Participant: ParticipantId{EchoParticipant} has received from Endpoint: 01.0f.44.59.33.e0.2b.cf.01.00.00.00|0.0.12.3 in topic: Topic{rt/chatter, std_msgs::msg::dds_::String_} the following payload: <Payload{00 01 00 00 0f 00 00 00 48 65 6c 6c 6f 20 57 6f 72 6c 64 3a 20 34 00 00}>
Echo Participant: ParticipantId{EchoParticipant} has received from Endpoint: 01.0f.44.59.33.e0.2b.cf.01.00.00.00|0.0.12.3 in topic: Topic{rt/chatter, std_msgs::msg::dds_::String_} the following payload: <Payload{00 01 00 00 0f 00 00 00 48 65 6c 6c 6f 20 57 6f 72 6c 64 3a 20 35 00 00}>
...