Node not receiving update after simulated time is update on /clock topic.

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Hello,

I am playing a bit with simulated time in ROS. I have one node that serves as the clock server, and another node that will do some calculations. At times it happens that if I start the calculator node, and then the clock server, the calculator node never gets the updated time.

More in detail: I have roscore running in one terminal, the clock server in a second, and the calculator in a third. For both clock server and calculator I do the following when running them

Terminal 2

rosparam set /use_sim_time True
rosrun package clock

Terminal 3

rosparam set /use_sim_time True
rosrun package calculator

The code for the clock is as follows:

#!/usr/bin/env python
import rospy
import time
from rosgraph_msgs.msg import Clock

def simulation_clock(simulation_duration, time_step):

    pub = rospy.Publisher('/clock', Clock, queue_size=10)
    rospy.init_node('clock_agent', anonymous=True)

    step = rospy.Time.now()
    msg = Clock()

    while not rospy.is_shutdown() and step.secs < simulation_duration:
        step.secs += 1
        msg.clock = step
        pub.publish(msg)
        time.sleep(time_step)
        print "Simulated time is: %d" % rospy.get_rostime().secs

if __name__ == '__main__':
    try:
        duration = 10000
        time_step = 1 #seconds 
        simulation_clock(duration, time_step)
    except rospy.ROSInterruptException:
        pass

The code for the calculator is as follows:

#!/usr/bin/env python
import rospy
from std_msgs.msg import String

class Agent():
    def __init__(self, ID, init_state):
        rospy.init_node('agent', anonymous=True)

        while rospy.Time.now().secs == 0:
            pass

        print "Simulated time is: %d" % rospy.get_rostime().secs

if __name__ == '__main__':
    try:
        instance = Agent(1, 0)
    except rospy.ROSInterruptException:
        pass

On the first start of roscore, if I run the calculator and then the clock I will get the updated time on the calculator line. However, if I shutdown the calculator and clock, and try to restart, the order matters, i.e., if I first start the clock and then the calculator, the latter will get the updated value. Whereas if I start the calculator and then the clock, the calculator doesn't get the updated clock value.

Any idea what's going on, what I am missing?

Thanks!

hw