Is there any kind of etiquette for when you can or cannot text someone?

It’s hard to know how intrusive your text may be to the person who is receiving it.

Is there sound on, or does their phone just buzz? Is the phone of the person you’re texting plugged in somewhere in the house, or is it sitting in bed with them?

If I happen to be awake at 4am, and I think of something I need to text to someone, can I send that text right then? Or do I run the risk of waking them up for texting at an inappropriate hour?

Are there set hours for texting? When I was growing up, we were never allowed to get phone calls after 9pm. Is that true of a texting convention, as well?

What are we doing here?