Laptop connected to roscore host, does not receive messages

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Hey,

I was having some problems setting up my wifi network with a laptop and a pandaboard. The pandaboard starts its own wifi network through hostapd and the laptop connects to that network. The ROS_MASTER_URI is correctly set (ROS_HOSTNAME too, to '192.168.2.1', but I'm not sure it's still required) to http://192.168.2.1:11311 (Pandaboard) and the laptop can indeed communicate with the roscore (doing for example rostopic list gives me the correct list of currently active topics).

However if I do the following command on the laptop :

rostopic pub -r 1 /test std_msgs/String hello

and

rostopic echo /test

on the pandaboard, no messages are received. If I switch 'roles', no messages are received either. If I send and echo on the pandaboard, it does display messages. If I send and echo on the laptop, no messages are displayed.

If I connect both to my home network and set the ROS_MASTER_URI to its local IP everything works fine, but I don't always have such a network available... Is there something wrong with my hostapd network?