wrong network adapter with InetAddressFactory.newNonLoopback()

Question

Hi,

the last days i tried to run android_tutorial_pubsub and ran into several problems.

First i had the problem that

NodeConfiguration nodeConfiguration = NodeConfiguration.newPrivate();

was executed, which won't let you connect from a different device.

So i changed it into something like NodeConfiguration.newPublic(InetAddressFactory.newNonLoopback().getHostAddress());

This gives you the first network device which is not a loopback device, but it does not check what device it is. For me it gave me vsnet0 instead of wlan0. So whenever i tried to connect to the subscribed topics or only executed rostopic info /chatter it would complain about not being able to connect. This is somehow expected as the ip address of vsnet0 is not in the same subnet as wlan0 and my other computers which run ROS.

I have now hardcoded the ip address for wlan0 from my android phone, but this is only usefull for my development environment, as i can't expect to have the same ip at other places.

The question now is how can i select the network device i want to use instead of just getting the first nonLoopback device?

Any idea or advice would be helpfull. Thank you.

Greetings, Markus

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Originally posted by bajo on ROS Answers with karma: 206 on 2012-10-08

Post score: 0

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Original comments

Comment by Lorenz on 2012-10-08:
Maybe that's a bug in rosjava. Consider filing a ticket on the corresponding bug tracker. To come up with a workaround, I suggest you have a look at the source code of InetAddressFactory: http://mediabox.grasp.upenn.edu/roswiki/doc/api/rosjava/html/InetAddressFactory_8java_source.html

Answer 1

This is a known bug: https://kforge.ros.org/appmanandroid/trac/ticket/26

I don't know why it's assigned to me. I don't think anyone is currently working on it.

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Originally posted by ahendrix with karma: 47576 on 2012-10-08

This answer was NOT ACCEPTED on the original site

Post score: 2

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Original comments

Comment by bajo on 2012-10-12:
I opened a ticket at http://code.google.com/p/rosjava/issues/list as this seems the correct place for it.

Answer 2

Hi, thank you both for your hints.

I managed to get the desired effect by changing the function newNonLoopback() so that it won't return PointToPoint interfaces like my phones radio network adapter vsnet0.

rosjava_core/rosjava/src/main/java/org/ros/address/InetAddressFactory.java

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public static InetAddress newNonLoopback() {
  for (InetAddress address : getAllInetAddresses()) {
    // IPv4 only for now.
    boolean p2p;
    try {
       p2p = NetworkInterface.getByInetAddress(address).isPointToPoint();
    } catch (SocketException e) {
      throw new RosRuntimeException(e);
    }   
    if (!address.isLoopbackAddress() && isIpv4(address) && (!p2p)) {
      return address;
    }   
  }   
  throw new RosRuntimeException("No non-loopback interface found.");
}

I will ask the maintainer of rosjava if he thinks it is wise to include in his repository so others can use it too.

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Originally posted by bajo with karma: 206 on 2012-10-10

This answer was ACCEPTED on the original site

Post score: 0

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Original comments

Comment by Lorenz on 2012-10-10:
Nice work. Best if you add a patch to the ticket that was referenced in @ahendrix answer or create a ticket on rosjava.googlecode.com with a patch attached.

Comment by damonkohler on 2012-10-10:
Please post issues to the rosjava issues list (http://code.google.com/p/rosjava/issues/list). I don't follow the trac tickets @ahendrix mentioned.

Comment by bajo on 2012-10-12:
I opened a ticket at http://code.google.com/p/rosjava/issues/list as this seems the correct place for it.