A sample ROS Service (Server)

sos_service.py

#! /usr/bin/env python
# remember to make this file executable (`chmod +x`) before trying to run it
import rospy
from std_srvs.srv import Trigger, TriggerResponse

def trigger_response(request):
    return TriggerResponse(
        success=True,
        message="Hey, roger that; we'll be right there!"
    )

rospy.init_node('sos_service') 
my_service = rospy.Service('/fake_911', Trigger, trigger_response)
rospy.spin()