Stopping Default TCP SITL Listener Prevents Accel 0 and Gyro 0 on UDP

[RbtsEvrwhr-Riley]

Describe the bug

On a WSL2 environment, we set up a simulation that required a UDP bridge (mav2xplane UDP https://github.com/RbtsEvrwhr-Riley/mav2xplane). By default it starts a TCP listener for the sim. Stopping this and starting UDP prevents sensors from acquiring.

To Reproduce

make px4_sitl none "simulator_mavlink stop" "simulator mavlink start udp"

Starts the UDP listener.

When it connects, accel 0 and gyro 0 will always provide invalid data, because they will not be updated on the correct ID. Baro and compass work as expected.

Expected behavior

The TCP sim that never connected should not set up any sensors.

Log Files and Screenshots

There is no flight, simulated flight could not start.

If you need more screenshots to reproduce I can get them but I need coffee.

Additional context

The following code block works as a workaround if added to px4-rc.simulator

This is not a fix, it just replaces starting TCP with starting UDP, then everything works.

`# otherwise start simulator (mavlink) module simulator_udp_port=$((14560+px4_instance))

# Check if PX4_SIM_HOSTNAME environment variable is empty
# If empty check if PX4_SIM_HOST_ADDR environment variable is empty
# If both are empty use localhost for simulator
if [ -z "${PX4_SIM_HOSTNAME}" ]; then

    if [ -z "${PX4_SIM_HOST_ADDR}" ]; then
        echo "INFO  [init] PX4_SIM_HOSTNAME: localhost"
        simulator_mavlink start udp $simulator_tcp_port
    else
        echo "INFO  [init] PX4_SIM_HOSTNAME: ${PX4_SIM_HOST_ADDR}"
        simulator_mavlink start udp -u "${PX4_SIM_HOST_ADDR}" "${simulator_tcp_port}"
    fi

else
    echo "INFO  [init] PX4_SIM_HOSTNAME: ${PX4_SIM_HOSTNAME}"
    simulator_mavlink start udp
fi`

[dagar]

If there's any bogus init happening in simulator_mavlink before there's a valid connection we can certainly fix it, but I would still suggest the proper fix here is to directly start only the desired interface in the first place.

[RbtsEvrwhr-Riley]

I cannot find any build option to change the init interface to UDP, having gone through source and had to modify it to allow such. TCP was hardcoded everywhere.

[RbtsEvrwhr-Riley]

The bug is definitely the init issue that's causing stopping and starting a new interface to break sensors, though; on the other hand, a menuconfig option or something to default UDP would be nice.