using multimaster on machine with lan and wifi

[Rimgaudas]

there is robot with board A and B roscore running on A multimaster runs on B A and B connected via Lan B has a wifi even running core on B doesn't solve a problem. is there a setting to choose which connection multimaster use? there is also possibility that multicast is disabled on the network. How can I test it?

[atiderko]

Hi,

1. you have to run roscore on A and B
2. you have to run master_discovery (a part of multimaster) on A and B
   • you can start it using node_manager (a part of multimaster)
3. if muticast is not supported by network master_discovery dies on start with an error
   • you can disable the usage of multicast by send_mcast
   • and if it starts but no other master_discovery nodes are discovered you can use robot_hosts to enter host to communicate with by unicast
4. You can bind master_discovery to an interface by interface or if you start master_discovery by node_manager add to the group the interface separated by @ e.g. 226.0.0.0@192.168.0.20

for other master_discovery parameters see the launch file in the package.

regards

[Rimgaudas]

I tried to run it on two laptops LAN works wifi doesn't

I am able to: -ping to each other -ping to 224.0.0.1 -master_discovery doesn't die on start with an error so it must be some kind of network settings I guess any idea how to test what is it ?

[atiderko]

you can try it with wireshark and look for heartbeat messages of master_discovery on udp.port ==11511 . Does receive each host from all other hosts these messages?

[mwswartwout]

I am facing a similar issue to this. I am trying to set this up over WiFi, however I do not control the network I am on and I believe that something with their security or NAT may be interfering with multicast. Can you explain more how the robot_hosts parameter should work?

I am enable to ping by IP and hostname from machine A to B. What I have done is run, on machine A: rosrun master_discovery_fkie master_discovery robot_hosts=MachineBHostname

And the opposite on Machine B. However they still do not discover each other. Is this the correct usage of robot_hosts?

Update to Original: Right now I have it working by editing the master_discovery.launch file to set the robot_hosts param. But I would like to know the syntax for setting that properly from the command line.

Also it works if I have send_mcast=True, but doesn't work if I have send_mcast=False like you said to set it to. If the hosts in robot_hosts are communicating via unicast, why do I not discover those hosts if multicast is disabled?

[atiderko]

Hi @mwswartwout,

the right command line to start on machine A: rosrun master_discovery_fkie master_discovery _robot_hosts:=[MachineBHostname] _send_mcast:=False

on machine B: rosrun master_discovery_fkie master_discovery _robot_hosts:=[MachineAHostname] _send_mcast:=False

if it does not work, try to start with additional parameter _log_level:=DEBUG. (You have to start master_discovery a second time to see the debug output). Perhaps you see what is going wrong or you post the log here.

The communication should work even if send_mcast is False.

regards, atiderko