Frozen MacOS terminal due ssh session timeout

To get out of a frozen terminal due to ssh timeout. Type the following keys:

enter (return key) ~.

Add the following to your .ssh/config file. It sends a signal to the server every 240 seconds to keep the session.

Host *
  ServerAliveInterval 240

Reference: http://www.metachunk.com/blog/dealing-osx-terminal-ssh-timeouts-0