Such as telnet the SSH protocol also has a control character, it’s the tilde (~).
If you for example want to kill a hanging SSH session just type ~. . With ~^Z you can suspend a running session and get back to your local machine. To reactivate it just type fg (yes, the SSH session is also just a job).
All supported escape sequences will be listed with ~? :
All sequences are of course only understood after a newline ;)