demi H's profile - activity

I have 2 robots, robot1(named hal) and robot2(named marvin), and I want to them to communicate.

I set every IP and hostname. robot1 can ping to itself and robot2 by their name(not IP). Also, robot2 can ping to itself and robot1 by their name. Of course, ssh between them works fine.

But there is a problem when they communicate. I'm using publisher-subscriber communicate model, and roscore is run in robot1.

When robot1 publish and robot2 subscribe message, it works fine. But when robot2 publish and robot1 subscribe message a callback function of robot1 isn't called. In 2nd case, publisher's getNumSubscribers always returns 0.

I followed this link : http://wiki.ros.org/ROS/Tutorials/Mul... , and I've already check whether there is misspelled topic or not.

Is there any possibility that this problem is related to firewalls?

I made 2 ROS node. One is for publishing and the other is for subscribing. However, sometimes receiving callback function is not called , even though a message is published.

Is the communication in publisher-subscriber is guaranteed?

Also, which kind of communication model is recommended when there are only 1 publisher and only 1 subscriber?(one-to-one)

Hi. I'm new to ROS and I'm working with ros cpp. I have a question.

I know that if I call ros::spin(), then it enter a loop, pumping callbacks. But there are certain function that I just want to call, only once in the whole execution time.(and probably at the beginning) Like initializing device(not ros::init), setting which device to use through stdin.

I know that i can use inifinite while loop, but I don't think that it's a good idea. Because ros::spin() is made for that purpose.

Is there any function to solve this problem?