Possible to use localhost for ROS and define an external IP?

[AlexisTM]

I am willing to start the multimaster at boot, but the network (Zerotier VPN) is not ready so roscore fails.

The VPN conncets to the internet via a 4G module, meaning that it takes at least 1 minute to be "ready".

I guess the master sync is using the ros master server directly, so it does not allow to use localhost to start and listen to/advertise another IP?

[atiderko]

Using localhost for communication between master_sync and roscore is not the problem. But if you use localhost in _ROS_MASTERURI it can lead to problems in communication to remote ROS nodes.

See http://wiki.ros.org/ROS/EnvironmentVariables

Is it possible to delay start of ROS nodes until VPN is ready?

[AlexisTM]

The VPN is a "virtual interface" so the systemd triggers are not working; The network is not ready when the virtual device wakes up.

Which of the following solutions would be best:

• Create a new FKIE application which first waits for the interface then run the main function of the original application
• Create an application that waits and returns when the interface has an IP, then run the normal roslaunch
• Isn't it possible to use default_cfg_fkie to run the next one once the first app returns? This requires the master to be running...

[atiderko]

Does the ROS Master start if VPN is not ready? If yes: it would be better to wait in the main function of FKIE application until VPN is ready. if no: you need an external script or something else what trigger a roslaunch start after VPN is ready.

_default_cfgfkie can delay a start of nodes or start these after a defined publisher topic is available. Each node in roslauch needs follow parameter:

    <param name="default_cfg/autostart/required/publisher" value="topic_name" />

[AlexisTM]

No, the master will not start before the IP is set. I'll go for the script checking the interface and starting the roslaunch as soon as ready

[AlexisTM]

For future reference, this it the solution I chose:

Service file: /lib/systemd/system/robot.service

[Unit]
Description=Robot bringup for the universe app manager and multimaster 

[Service]
User=alexis
Group=alexis
ExecStart=/usr/share/bringup.sh

[Install]
WantedBy=multi-user.target

Bringup script: /usr/share/bringup.sh

#!/bin/bash

# Wait until zerotier network is ready using python one-liner
FOUND_IP=$(python -c "import socket; import fcntl; import struct; from time import sleep

def get_ip_address(ifname):
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    return socket.inet_ntoa(fcntl.ioctl(
        s.fileno(),
        0x8915,  # SIOCGIFADDR
        struct.pack('256s', ifname[:15])
    )[20:24])

while True:
  try:
    print get_ip_address('ztuzethfie')
    break
  except: 
    sleep(0.1)")
# End of python

bash -c "source /home/alexis/rossetup.bash && ROS_IP=$FOUND_IP ROS_HOSTNAME=$FOUND_IP ROS_MASTER_URI=http://$FOUND_IP:11311 stdbuf -oL roslaunch platform bringup_robot.launch"

[atiderko]

@AlexisTM thank you for sharing!