@Maximus5 I test emacs on local machine and remote machine. They suffer the same problem. The remote one can be used normally on my mac with iterm.
I think that C-@ and C-/ have not been sent into the program.
Ctrl+/ never worked for me. Even from RealConsole. If don't know why but this is a question for another place.
But the Ctrl+_ (which is actually Ctrl+Shift+- on my keyboard layout) is working properly.