If you receive a short message from a strange number: Are you busy recently? Is everything all right? . Will you write back? Or how to deal with it?

Check the ownership of the mobile phone first to see where it belongs, and then you can probably judge where it belongs and what friends it is. Then wait, if you really know him, I believe that if you don't reply, he will send another note explaining who he is. If you don't, you must not know him. You can also call your friend's old number and ask if you changed your number.