One Way Broadcasting Issues
Problem
You are trying to connect two machines and finding the pubsub communications only go one way (echo from one side works, but reversing the communication, it fails on the other side).
Ros nodes generally need some help providing the correct information about which interface they are operating on to the ros master. It probably could be smarter than it is, but if you use the following, it will help roscpp nodes resolve to each other.
Solution
Using IP Addresses
If you have fixed ip addresses, set the ROS_IP variable on both machines and make sure you use the ip addresses for ROS_MASTER_URI as well.
Master (192.168.1.100):
export ROS_MASTER_URI=http://localhost:11311 export ROS_IP=192.168.1.100
Client (192.168.1.101)
export ROS_MASTER_URI=http://192.168.1.100:11311 export ROS_IP=192.168.1.101
Using Hostnames
Useful if you have dhcp settings, or you are spanning multimaster across several network interfaces.
Master (foo):
export ROS_MASTER_URI=http://foo:11311 export ROS_HOSTNAME=foo
Client (192.168.1.101)
export ROS_MASTER_URI=http://foo:11311 export ROS_HOSTNAME=bar
If you're doing this with static ips, make sure the hostnames are stored in both machine's host's files (/etc/hosts or C:\WINDOWS\system32\drivers\etc\hosts.
Master:
192.168.1.101 bar
Client
192.168.1.100 foo
OR ensure they are being served by your lan's DNS Server.
Other
This does not work for a virtual machine (e.g. virtualbox) running NAT. Use bridged networking instead.
See also:
