Cela peut par exemple vous servir pour gérer ou retrouver vos tunnel.
Extrait du man :
ESCAPE CHARACTERS
When a pseudo-terminal has been requested, ssh supports a number of func-
tions through the use of an escape character.
A single tilde character can be sent as ~~ or by following the tilde by a
character other than those described below. The escape character must
always follow a newline to be interpreted as special. The escape charac-
ter can be changed in configuration files using the EscapeChar configura-
tion directive or on the command line by the -e option.
The supported escapes (assuming the default `~') are:
~. Disconnect.
~^Z Background ssh.
~# List forwarded connections.
~& Background ssh at logout when waiting for forwarded connection /
X11 sessions to terminate.
~? Display a list of escape characters.
~B Send a BREAK to the remote system (only useful for SSH protocol
version 2 and if the peer supports it).
~C Open command line. Currently this allows the addition of port
forwardings using the -L, -R and -D options (see above). It also
allows the cancellation of existing port-forwardings with
-KL[<em>bind_address</em>:]<em>port</em> for local, -KR[<em>bind_address</em>:]<em>port</em> for re-
mote and -KD[<em>bind_address</em>:]<em>port</em> for dynamic port-forwardings.
!<em>command</em> allows the user to execute a local command if the
PermitLocalCommand option is enabled in <a href="http://man.openbsd.org/">ssh_config(5)</a>. Basic
help is available, using the -h option.
~R Request rekeying of the connection (only useful for SSH protocol
version 2 and if the peer supports it).