Is it possible to make one node both a publisher and a subscriber?  That is, would the following code fragment work?


rospy.init_node('relay')
pub = rospy.Publisher('talker', someMsg)
oldMessages = set()

def callback(data):
	if not data in oldMessages:
		pub.publish(data)	
	oldMessages.add(data)	

sub = rospy.Subscriber('listener', someMsg, callback)

if __name__ == '__main__':
	rospy.spin()

Thanks,
Cem Karan