How to Send large amount of remaining files to a server using SCP. (Both Linux Server has similar files and I want to avoid overwrite.)

I have sent a large number of files using SCP previously and when I send those files the Internet connection suddenly dropped.

scp -r * next_server_username@ip_address_of_receiver:receiver_path

now, How can I verify previously sent files and find the remaining files to securely transfer? How can I avoid rewriting?