How can I handle CONNECTED and DISCONNECTED events?

[Son Tran]

Hello!

I am using wpa_supplicant to connect to wireless networks. Now, I want to
use OpenVPN to connect to my VPN, and I want to start OpenVPN service
when wpa_supplicant connects to a network and stop OpenVPN service when
wpa_supplicant disconnects to a network. How can I solve this problem? I
use systemd to start wpa_supplicant at boot.

I appreciate any help!

Thanks!
Son