rmw_fastrtps: RasperryPi3 Wireless communication problem

Note: This was initially reported by @codebot by e-mail to eProsima. It is posted here following a suggestion by @dirk-thomas

Bug report

Required Info:

• Operating System:
  • Ubuntu 18.04
• Installation type:
  • binaries
• Version or commit hash:
  • dashing (ros-dashing-rmw-fastrtps-cpp is 0.7.5-1bionic)
• DDS implementation:
  • Fast-RTPS

Steps to reproduce issue

# On Machine 1 (x86 workstation with Ubuntu 18.04 and ROS 2 Dashing)
ros2 run examples_rclpy_minimal_publisher publisher_old_school

# On Machine 2 (Raspberry Pi 3 with Ubuntu 18.04 and ROS 2 Dashing)
ros2 run examples_rclpy_minimal_subscriber subscriber_old_school

Expected behavior

Strings published from Machine 1 start printing on the console of Machine 2, after allowing a few seconds for discovery and connection.

Actual behavior

Usually, nothing is printed on the console of Machine 2. If left to run for a long time, sometimes after ~3 to ~5 minutes a few strings will print to the console intermittently, but usually (probably 90-99% of the time) it is not receiving messages. I don’t know if this is due to WiFi jitter/latency/packet-drops on the RPi3, or the relatively slow CPU and I/O on the RPi3 causing some timeouts to be missed, or what’s going on exactly. This behavior appears “sometimes” on laptops on WiFi, but it is more hit-and-miss. With the RPi3 it’s typically much easier to reproduce the issue.

Additional information

Router model (in case it matters): TP-Link Archer C4000 Machine 1: connected via (wired) Gigabit Ethernet Machine 2: connected via the RPi3 built-in WiFi, which is not super awesome