That makes some sense to me. Thanks.
Can kasa python use unicast to control the plug if the ip is given?

--host IP_ADDRESS should do the trick

Please show me the correct syntax for using --host IP_ADDRESS or point to a doc that explains it. All I need to do is turn the plug on and off.
Below is what I tried. It works to print the status, but plug.turn_on() produces runtime warnings and doesn't turn the plug on.

import asyncio
from kasa import SmartPlug
from pprint import pformat as pf
plug = SmartPlug("192.168.0.20")
asyncio.run(plug.update())
print("Hardware: %s" % pf(plug.hw_info))
print("Full sysinfo: %s" % pf(plug.sys_info))
print("Current state: %s" % plug.is_on)
plug.turn_on()

As all actions are coroutines (defined with async def), you need to schedule their execution. In your example, executing asyncio.run(plug.turn_on()) should do the trick! To do the same inside another coroutine, you need to use await like await plug.turn_on().

OK, this code runs on my network: Win 10 computer on ethernet and the plug on WiFi.

In another location, same setup: Win10 on ethernet and the plug on WiFI. Program hangs. Note: the computer can ping the plug with no problem. But SmartPlug(IP) can't find it. Seems like it should if it uses unicast like ping does???

import asyncio
import time
from kasa import SmartPlug
from pprint import pformat as pf
f = open("IP.txt")
IP=f.readline()
print("IP.txt = ", IP)
plug = SmartPlug(IP)
asyncio.run(plug.update())
print("Hardware: %s" % pf(plug.hw_info))
print("Full sysinfo: %s" % pf(plug.sys_info))
while(True):
	asyncio.run(plug.turn_on())
	asyncio.run(plug.update())
	print("Current state: %s" % plug.is_on)
	time.sleep(1)	
	asyncio.run(plug.turn_off())
	asyncio.run(plug.update())
	print("Current state: %s" % plug.is_on)
	time.sleep(1)

I'm running into the same issue, were you able to figure it out?