A list of IPs for mtalk.google.com(aka Google FCM service) that connectable from Mainland China
142.250.111.188
142.250.101.188
142.250.31.188
172.253.62.188
142.250.111.188
172.253.122.188
142.250.115.188
172.217.194.188
64.233.188.188
108.177.97.188
108.177.125.188
74.125.203.188