listener_subscribe_notify.py

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#!/usr/bin/env python
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## talker that receives notification of new subscriptions

PKG = 'rospy_tutorials' # this package name
NAME = 'talker_callback'

import roslib; roslib.load_manifest(PKG) 

import sys

import rospy
from std_msgs.msg import String

class ChatterListener(rospy.SubscribeListener):
    def peer_subscribe(self, topic_name, topic_publish, peer_publish):
        print "a peer subscribed to topic [%s]"%topic_name
        
        str = "Hey everyone, we have a new friend!"
        print str
        topic_publish(String(str))
        str = "greetings. welcome to topic "+topic_name
        print str
        peer_publish(String(str))
        
    def peer_unsubscribe(self, topic_name, numPeers):
        print "a peer unsubscribed from topic [%s]"%topic_name
        if numPeers == 0:
            print "I have no friends"
    
def talker_callback():
    pub = rospy.Publisher("chatter", String, ChatterListener())
    rospy.init_node(NAME, anonymous=True)
    count = 0
    while not rospy.is_shutdown():
        str = "hello world %d"%count
        print str
        pub.publish(String(str))
        count += 1
        rospy.sleep(0.1)
        
if __name__ == '__main__':
    try:
        talker_callback()
    except rospy.ROSInterruptException: pass