Add port forwarding to running SSH sessions
Recently I got a tip about subsequent adding of port forwardings to SSH Sessions without logout/login. As I work a lot with cloud technology and therefore use openssh very frequently, I found this very handy and use it several times a day.
Basically you enter openssh’s escape sequence
~ (only recognized immediately after newline), followed by
Shift + C. This should give you a
ssh> prompt. After that, you can use the port forwarding command option syntax without the leading dash.
user@sshhost $ ~C ssh> L8080:localhost:8080 Forwarding port. user@sshhost $
You can also cancel an existing port forwarding.
user@sshhost $ ~C ssh> KL8080 Canceled forwarding. user@sshhost $
If you are connected through multiple nested SSH connections, you can choose to modify the next deeper nested connection by adding one more
~ escape character.
There are additional useful escape sequences (for example to terminate hanging connections by
user@sshhost $ ~? Supported escape sequences: ~. - terminate connection (and any multiplexed sessions) ~B - send a BREAK to the remote system ~C - open a command line ~R - request rekey ~V/v - decrease/increase verbosity (LogLevel) ~^Z - suspend ssh ~# - list forwarded connections ~& - background ssh (when waiting for connections to terminate) ~? - this message ~~ - send the escape character by typing it twice (Note that escapes are only recognized immediately after newline.)