If you need a signal both if the window was closed and opened you can buy this sensor:
https://www.aliexpress.com/item/Free-shipping-Wireless-window-and-door-magnetic-sensor-open-detector-1527-chips/32334214010.html
It is based on a 1527 Chip.
Open the rear cover and connect these pins with a solder point:

@amitach I have the same setup and I use a MQTT-Client for testing: http://www.jensd.de/wordpress/
You have to stop OpenHAB, because only one connection to the gateway is possible.
Usage:

• start client
• create a profile: Extras / Connection Profiles
• connect with this profile
• click button "Subscribe"
• choose "Topic" : # (see wildcards: http://mosquitto.org/man/mqtt-7.html )
• click button "Subscribe" (on the right from field "Topic"

Now you see all messages from your sensor.

10-10-0-0
 |  | | |
 |  | | Id of Destination node
 |  | ID of next node
 |  Id of last node this message passed
 Id of sender node (origin)


s = child-sensor-id, 255 für "interne" Messages
c = message-type
t = sub-type
pt = payload-type (see MyMessage.h)
l = length of payload

Values c,t,pt: see http://www.mysensors.org/download/serial_api_13

@Jransom2 Unless I'm very much mistaken there is no temperatur message in the lines after "Started!".
During the last day several users of OpenHAB / MQTT had a problem with the first connection. A good tool for debugging is the MQTT client from jerady.
See my posting here: http://forum.mysensors.org/topic/953/how-to-know-the-node-ids-assigned-by-the-mqtt-gateway-to-the-sensors/

For more than two switches see: http://www.gammon.com.au/forum/?id=11091
I would add a hardware debouncing (R/C) to avoid the problems mentioned in the article.