# ROS Container Communication
> [name=楊育陞([e-mail])]
## Introduction
本篇處理以下通訊情況：
1. 同裝置，兩個以上ROS2 container通訊
2. 跨裝置，兩個以上ROS2 container通訊
3. 同裝置，ROS2 container和ROS1通訊
4. 跨裝置，ROS2 container和ROS1通訊

## Scenario 1 & 2
> 同裝置/跨裝置，兩個以上ROS2 container通訊

因為ROS2使用DDS架構，只要ROS2 nodes在同網域下就能直接互相通訊，而docker在執行container時預設是使用和host隔離的網域，所以我們要另外在執行container時加入tag:

--net=host \
--pid=host

container就會使用和host相連的network，網路內的ROS2 node就能互相通訊

### Test
使用以下指令測試：

ros2 run demo_nodes_cpp listener
ros2 run demo_nodes_cpp talker

在以下狀況可以順利通訊：
#### case 1
+ device 1: 敞篷桌機 -> container: orca_docker
+ device 2: Orin -> container: isaac_ros (內建連host，不用額外加指令)
(在同wifi底下)

#### case 2
+ device 1: 敞篷桌機 -> ros2 (沒container包裝)
+ device 2: Orin -> container: isaac_ros (內建連host，不用額外加指令)
(在同wifi底下)

#### case 3
+ device 1: 敞篷桌機 -> container: orca_docker
+ device 1: 敞篷桌機 -> container: orsf/ros

#### case 4 (待測)
+ device 1: Rpi -> container:
+ device 2: Orin -> container:
(有線連接)

## Scenario 3
> 同裝置，ROS2 container和ROS1通訊

使用ROS2的[ros1_bridge](https://github.com/ros2/ros1_bridge)這個package，建立ROS1和ROS2之間的通訊。
以下為使用[ros:eloquent-ros1-bridge](https://hub.docker.com/layers/library/ros/eloquent-ros1-bridge/images/sha256-0040f128fdbdee7f904ec9db6f5ae93a4ca9ec1e756c5dabb33c7766fa4e6a2c?context=explore)這個image建立rpi上的bridge container，
repo: https://github.com/NCTU-AUV/orca_ros_bridge.git
(因為rpi架構為armv7，ros2版本選擇eloquent，其他架構請參考[docker hub](https://hub.docker.com/_/ros/tags))
### Usage
1. build container

git clone https://github.com/NCTU-AUV/orca_ros_bridge.git
cd orca_ros_bridge
./scripts/build.sh

2. excute bridge

./scripts/run

## Scenario 4
> 跨裝置，ROS2 container和ROS1通訊

結合scenario 2 和 3，就能實現跨裝置的ROS2 container和ROS1通訊
https://youtu.be/iKkuG8wfYi4

### Reference
https://husarnet.com/blog/ros2-docker
https://azole.medium.com/webconf2023-docker-%E5%85%A5%E9%96%80-101-fae89170553a
https://docs.docker.com/network/network-tutorial-standalone/
https://answers.ros.org/question/358453/ros2-docker-multiple-hosts/
https://community.rti.com/kb/how-use-rti-connext-dds-communicate-across-docker-containers-using-host-driver
https://hub.docker.com/_/ros/
https://github.com/ros2/ros1_bridge/blob/master/README.md
https://github.com/ros2/ros1_bridge/blob/master/doc/index.rst