SSH - add port forwardings on a live connection with EscapeChar

categories:

• SSH

Excerpt from the man page :

The interesting part is in bold.

<code>When a pseudo-terminal has been requested, ssh supports a number of functions 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 character can be changed in configuration
files using the EscapeChar configuration 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).

<strong>~C      Open command line.  Currently this allows the addition of port forwardings
        using the -L and -R options (see above).  It also allows the cancellation of
        existing remote port-forwardings using -KR[bind_address:]port.  !command
        allows the user to execute a local command if the PermitLocalCommand option is
        enabled in ssh_config(5).  Basic help is available, using the -h option.</strong>

~R      Request rekeying of the connection (only useful for SSH protocol version 2 and
        if the peer supports it).
</code>

EscapeChar also allows disconnection of an SSH session, for example when it is hanging and is not giving you the prompt back (~.).