1. If you feel the same way about him, you can reply: "I miss you too. I hope we can meet soon. "
If you just want to respond to him politely, you can reply "Thank you for telling me this. I am glad to hear that you miss me. "
If you think his behavior is a little inappropriate, you can reply: "I know you miss me, but your current state is not suitable for talking about it." You need to have a rest first. "
If you don't want to have further contact with him, you can reply: "Thank you for your thoughts, but I can't respond to your feelings now."
It should be noted that no matter what you reply, you need to be respectful and polite, and at the same time, you should take into account the state and feelings of the other party.