ROS Empty Topics on goroslib node

[soufi]

Hi,

I use the goroslib with mavros on arducopter.
I'm having a weird issue and i'm hoping you could provide some guidance, so here's what's happening:
I'm running a SITL (simulator) on virtualbox along with a mavros master node. I use the following launch file to run with roslaunch:

 <launch>
	<!-- vim: set ft=xml noet : -->
	<!-- example launch script for ArduPilot based FCU's -->

	<arg name="fcu_url" default="udp://192.168.0.22:14550@14555" />
	<arg name="gcs_url" default="" />
	<arg name="tgt_system" default="1" />
	<arg name="tgt_component" default="1" />
	<arg name="log_output" default="screen" />
	<arg name="fcu_protocol" default="v2.0" />
	<arg name="respawn_mavros" default="false" />

	<include file="$(find mavros)/launch/node.launch">
		<arg name="pluginlists_yaml" value="$(find mavros)/launch/apm_pluginlists.yaml" />
		<arg name="config_yaml" value="$(find mavros)/launch/apm_config.yaml" />

		<arg name="fcu_url" value="$(arg fcu_url)" />
		<arg name="gcs_url" value="$(arg gcs_url)" />
		<arg name="tgt_system" value="$(arg tgt_system)" />
		<arg name="tgt_component" value="$(arg tgt_component)" />
		<arg name="log_output" value="$(arg log_output)" />
		<arg name="fcu_protocol" value="$(arg fcu_protocol)" />
		<arg name="respawn_mavros" value="$(arg respawn_mavros)" />
	</include>
</launch>

Then I connect my goroslib program with the master node and read topics etc .... this usually works.

Now sometimes when I change my local network (and go to a friend's house for example), my goroslib connects to the master node without any issues, but no topic is triggered ... nothing happens....
I tried to run the goroslib program from my raspberrypi for example and connect to the master node ... nothing happens ... topics are empty ...

Would you have any idea why this could happen ?

Thank you !

[soufi]

so I used the following code :

package main

import (
	"fmt"

	"github.com/aler9/goroslib"
	"github.com/aler9/goroslib/pkg/msgs/sensor_msgs"
)

func onMessage(msg *sensor_msgs.BatteryState) {
	fmt.Printf("Incoming: %+v\n", msg)
}

func main() {
	// create a node and connect to the master
	n, err := goroslib.NewNode(goroslib.NodeConf{
		Name:          "goroslib_sub",
		MasterAddress: "192.168.0.22:11311",
	})
	if err != nil {
		panic(err)
	}
	defer n.Close()

	sub, err := goroslib.NewSubscriber(goroslib.SubscriberConf{
		Node:     n,
		Topic:    "/mavros/battery",
		Callback: onMessage,
		// Protocol: goroslib.UDP,
	})
	if err != nil {
		panic(err)
	}
	defer sub.Close()

	// freeze main loop
	select {}
}

so I run this code from the raspberry pi, topics are not updated.
I run it from my computer, I receive topics ...

it's just bugging me, I can't understand how is this possible :/

any thoughts ?

[soufi]

I am able to get topics using rostopic echo /mavros/battery (by setting up the ROS_MASTER_URI to the distant virtualbox machine), but nothing comes from the code above ... though I am able to list the nodes, topics etc using goroslib... but topics ... nothing .... still can't figure out what could be the reason. Any hint is much appreciated.
thanks

[soufi]

It seems that when using the IP address, topic subscription doesn't work, when I flipped the MasterAddress and used hostname instead (that I added to /etc/hosts) it worked just fine !

[aler9]

Hello, i checked the code repeatedly, and i can say that MasterAddress is solved (converted into IP) once, then this IP is used throughout the entire library. Anyway, an error report system must be implemented.

[soufi]

Thank you @aler9
I am interested in helping with the library :) I'll be getting in touch when needed !

[aler9]

BTW, an error report system has been implemented (it's been easier than i thought): now goroslib prints on the console any error it encounters, especially when it's unable to connect to something or a message has a wrong checksum.