Joke Collection Website - Blessing messages - How do I know when the other party's mobile phone is turned on?

How do I know when the other party's mobile phone is turned on?

There are the following methods:

Call each other, and then set up a small communication secretary, as long as there is a signal will prompt.

Some mobile phones have information reporting function. As long as you use this function, you will know if the other party is turned on.

Use software, such as texting, checking ping, and sending it to the other party's mobile phone, so that the other party can know whether the other party is turned on without knowing it.