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Austin
Asked: 2018-06-20 10:03:10 +0800 CST

List ports forwarded by myself from ssh?

  • 772

If I connect to a server like so:

JP_PORT=$(shuf -i 8895-9100 -n 1)
TB_PORT=$(shuf -i 6010-6200 -n 1)
ssh -Y -L ${JP_PORT}:127.0.0.1:${JP_PORT} -L ${TB_PORT}:127.0.0.1:${TB_PORT} <host>

Once connection is established, is there any terminal command that will return the list of ports I forwarded?

command-line ssh port-forwarding

3 Answers

  1. Best Answer

    You can list via lsof

    sudo lsof -i -n

    You may use grep to filter results

    sudo lsof -i -n  | grep ssh
    • 6

  2. If it is enough to list only the forwarded connections that are actually used, and if your session is interactive (like in your case), you can use the ~# escape within the ssh session. Just type enter~#.

    $ ssh -L1234:localhost:22 localhost
seb@localhost's password: 
Welcome to Ubuntu 18.04 LTS (GNU/Linux 4.15.0-23-generic x86_64)
$ ~#
The following connections are open:
  #2 client-session (t4 r0 i0/0 o0/0 fd 7/8 cc -1)
  #3 direct-tcpip: listening port 1234 for localhost port 22, connect from 127.0.0.1 port 37238 to 127.0.0.1 port 1234 (t4 r1 i0/0 o0/0 fd 10/10 cc -1)

    This will also list forwardings that were added later within the session using escape commands, and thus are not appearing on the command line.

    Try ~? for other useful commands inside the ssh session. See also the section on ESCAPE CHARACTERS in the ssh manual page.

    • 3

  3. There's a couple more ways to list ssh's connections/tunnels. Firstly one can use netstat (p show process name (sudo needed), ip - show IP connections):

    sudo netstat -ap --ip | grep ssh

    Secondly one can also use the socket stats command ss (p - show process name (sudo needed), e - extended socket info for userid, t - TCP connections):

    sudo ss -pet | grep ssh

    Note: Local (-L) ssh tunnels are not created on the server until the something on the client side has initiated a connection to the local port - only then will the tunnel be set up on the server side and be visible by these methods or any of the other answers.

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