that is a feature request. It could be, that someone before me, already requested it, but I can not read
the message because it is in Japanese and I can only recognize the Header and that is probably similar.
An extremly useful enhancement for TerraTerm would be the support from the Mosh Protocol
A short description from Mosh? (Copied from Web page)
Remote terminal application that allows roaming, supports intermittent connectivity, and provides intelligent local echo and line editing of user keystrokes.
Mosh is a replacement for SSH. It's more robust and responsive, especially over Wi-Fi, cellular, and long-distance links.
It requires SSH for Authentication and then switches to UDP....
The source is available from https://github.com/keithw/mosh
and the License is now GPL.
They are already Cygwin binaries and sources available
If you need someone for testing please let me know!!