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.
##################################
# CONFIGURATION VERSION
version: v3.0 # 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
- name: EchoParticipant # 6
kind: 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 # 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 does not require further configuration than name and kind.
- name: EchoParticipant # 6
kind: 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_tool>/share/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_tool>/share/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}>
...