rmw_email

ROS 2 over email. rmw_email contains a middleware that sends & receives strings over email and an RMW implementation that allows ROS 2 to use this middleware to exchange messages.

For an overview of the motivation and process behind this project, see this blog post: christophebedard.com/ros-2-over-email.

1. Overview
2. Packages
3. Supported features
   1. Platform support
4. Performance
5. How to use
6. Configuration
7. Tracing
8. Logging
9. email examples

Overview

rmw_email_cpp uses type support introspection to convert messages to YAML objects. This is done for both C and C++ type supports using the dynmsg package. The YAML objects are then converted to strings.

Those strings are sent via email using the email package. The topic name is used as the email subject; the email body contains the YAML string representing the message. Messages can therefore easily be read.

To receive messages, this process is repeated in the opposite direction.

Successive messages on the same topic generally end up in the same email thread (depending on the client). Service responses are email replies to the corresponding email request (this is handled by email).

email also has an intraprocess communication mode to bypass actually sending and receiving emails.

Packages

This repository contains a few packages:

• email: simple publish/subscribe & service middleware using emails to exchange strings
  • See the API documentation.
  • See the design document (rendered version).
  • This package claims to be in the Quality Level 4 category, see the Quality Declaration for more details.
  • 
• email_examples: various examples using email
  • See email examples.
  • This package claims to be in the Quality Level 4 category, see the Quality Declaration for more details.
• rmw_email_cpp: ROS 2 rmw implementation using email as the middleware
  • See supported features.
  • This package claims to be in the Quality Level 4 category, see the Quality Declaration for more details.
  • 

Supported features

The following table shows the features currently supported/unsupported by rmw_email_cpp.

Platform support

rmw_email was primarily developed on Ubuntu. However, it should work on macOS and Windows without too much effort. See REP 2000.

Performance

We can use performance_test to compare the performance of rmw_email_cpp to another RMW implementation.

See the perf_test.sh and perf_plot.sh scripts to run performance_test and generate a plot like the one above.

How to use

1. Clone this repo into your ROS 2 workspace

```sh $ cd ~/ws/src/

File truncated at 100 lines see the full file

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