Unable to detect ROS master across Wifi and Ethernet

Hi,

I have a PC connected to both Wifi and Ethernet. A ROS master is running in Wifi network A and another ROS master is running in Ethernet network B. At PC, I can ping both machines where ROS master is running. However, I am unable to establish communications between two ROS masters.

Currently, when I run the following in my laptop.

export ROS_MASTER_URI="http://10.66.171.1:11311" # ROS_MASTER_URI for ROS Master on network A
rosrun master_discovery_fkie master_discovery

I get

[INFO] [WallTime: 1572328934.230123] ROS Master URI: http://10.66.171.1:11311
[INFO] [WallTime: 1572328934.261932] Check the ROS Master[Hz]: 1
[INFO] [WallTime: 1572328934.262249] Heartbeat [Hz]: 0.02
[INFO] [WallTime: 1572328934.262452] Active request after [sec]: 60
[INFO] [WallTime: 1572328934.262631] Remove after [sec]: 300
[INFO] [WallTime: 1572328934.262809] Robot hosts: []
[INFO] [WallTime: 1572328934.262983] Approx. mininum avg. network load: 1.36 bytes/s
[INFO] [WallTime: 1572328934.275997] Start RPC-XML Server at ('0.0.0.0', 11611)
[INFO] [WallTime: 1572328934.276577] Subscribe to parameter /roslaunch/uris
[INFO] [WallTime: 1572328934.302547] + Bind to specified unicast socket @(137.132.82.147:11511)
[INFO] [WallTime: 1572328934.302908] Create multicast socket at ('226.0.0.0', 11511)
[INFO] [WallTime: 1572328934.624952] Detected master discovery: http://localhost:11611
[INFO] [WallTime: 1572328934.729224] Added master with ROS_MASTER_URI=http://10.66.171.1:11311/

And then I run the following in another terminal:

export ROS_MASTER_URI=http://137.132.82.147:11311 # ROS_MASTER_URI on network B
rosrun master_discovery_fkie master_discovery

I get:

[INFO] [WallTime: 1572329338.024654] ROS Master URI: http://localhost:11311
[INFO] [WallTime: 1572329338.041032] Check the ROS Master[Hz]: 1
[INFO] [WallTime: 1572329338.041357] Heart beat [Hz]: 0.02
[INFO] [WallTime: 1572329338.041591] Active request after [sec]: 60
[INFO] [WallTime: 1572329338.041808] Remove after [sec]: 300
[INFO] [WallTime: 1572329338.042024] Robot hosts: []
[INFO] [WallTime: 1572329338.042234] Approx. mininum avg. network load: 1.36 bytes/s
[WARN] [WallTime: 1572329338.050148] Error while start RPC-XML server on port 11611: [Errno 98] Address already in use Try again...
[WARN] [WallTime: 1572329339.051930] Error while start RPC-XML server on port 11611: [Errno 98] Address already in use Try again...
[WARN] [WallTime: 1572329340.053891] Error while start RPC-XML server on port 11611: [Errno 98] Address already in use Try again...
[WARN] [WallTime: 1572329341.055901] Error while start RPC-XML server on port 11611: [Errno 98] Address already in use Try again...
[WARN] [WallTime: 1572329342.058117] Error while start RPC-XML server on port 11611: [Errno 98] Address already in use Try again...

My current multicast setting and ip forward setting is as follows: cat /proc/sys/net/ipv4/ip_forward -> 1 # ip forward is enabled cat /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts -> 1 # multi cast not enabled

I deeply appreciate if you can help with this issue. Thank you a lot in advance.

[atiderko]

In this case, the solution is a little more complicated.

Since the master_sync is not running on the same host with ROS Master the check for hostname fails. It was already addressed in issue #106. There is a solution for this: you can set check_host to false while start master_sync.

But you have to use the current github version of multimaster. In the current version all packages are renamed from fkie to fkie.

[atiderko]

Nice to hear it works for you!

In usual case the master_discovery and ROS Master are running at the same host. So they address should be equal. Your scenario is different from usual case. So if your ROS communication works well you can ignore this warning.