listenerpublisher.py

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#!/usr/bin/env python
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## Utility node for testing. Listens to chatter and when it gets a
## message it starts rebroadcasting on 'listenerpublisher'.  Unlike
## the normal listener, listenerpublisher is NOT anonymous.

from __future__ import print_function

import sys
import rospy
from std_msgs.msg import *

_publishing = False
_pub = None
def start_publishing():
    global _pub
    if _pub is not None:
        return
    print("registering onto listenerpublisher")
    _pub = rospy.Publisher("listenerpublisher", String)
    
def callback(data):
    print(rospy.get_caller_id(), "I heard %s"%data.data)
    start_publishing()
    print("publishing", data.data)
    _pub.publish(String(data.data))
    
def listener():
    rospy.init_node("listenerpublisher")
    rospy.Subscriber("chatter", String, callback)
    rospy.spin()
        
if __name__ == '__main__':
    listener()