The ssh command line client offers quite a few options not many users are aware of. Once all sessions previously using the forwarded port have ended the forwarding definition is no longer listed in the output of ~#. Ssh> KL5510 # remove local port forwarding definition You can even stop forwarding sessions on the command line: ~]$ # hit ~C again to enter the command line If you really need to know ports in LISTEN status you have to use lsof or netstat and related tools. This is close to Putty’s behaviour, but not a match. Unfortunately the forwarded port is only shown once an initial connection is established. In the above output line #3 indicates the browser session connecting to EM Express. Your client session is always present as line #0. Escape character ~# displays currently active, forwarded ports: ~]$ ~# hit ~ followed by # to display the information Should you find yourself in a situation where you’re unsure which ports you have forwarded, you can find out about that, too. In other words, you connect to Enterprise Manager Express. If you point a supprted web browser to the connection request is forwarded to server2’s port 5510. Ssh> L5510:server2:5510 # add a local port forwarding ruleĪs soon as you see the message “Forwarding port” you are all set, provided of course the ports are defined correctly in your forwarding rule and there’s no service running on port 5510 on your laptop. ~]$ # hit ~ followed by C to open the command line With that information at hand the port forwarding rule can be added to the currently established SSH session. SQL> select dbms_xdb_config.gethttpsport from dual Connected to the PDB in question, you can use DBMS_XDB_CONFIG to get the HTTPS port number like so: SQL> show con_name The first step is to find out which port is used for EM Express. Assuming you would like to use port-forwarding to tunnel the Oracle Enterprise Manager (EM) Express port for a Pluggable Databases (PDBs) to your local laptop. Basic help is available, using the -h option. !command allows the user to execute a local command if the PermitLocalCommand option is enabled in ssh_config(5). It also allows the cancellation of existing port-forwardings with -KLport for local, -KRport for remote and -KDport for dynamic port-forwardings. Currently this allows the addition of port forwardings using the -L, -R and -D options (see above). It opens a command line and allows you to make changes to the connection. The most interesting escape sequence from this article's point of view is ~C. The ssh(1) man page dedicates an entire section to them. Once established you can control the behaviour of your SSH session using escape characters. Wouldn’t it be nice if you could simply add a port forwarding rules just like with Putty? Putty-like port-forwarding Occasionally you may not know in advance which ports to forward, and establishing a new session might not be convenient. For example: ssh -i ~/.ssh/remoteuser -L 8080:server2:8080 Throw in the -N flag and you don’t even open your login shell! That’s a very convenient way to enable port forwarding. You can specify either the -L or -R flag (and -D for completely dynamic port-forwarding using SOCKS - which is not in scope of this article) when establishing a SSH session to a remote host, specifying how ports should be forwarded. Although no research has been conducted to find out when exactly dynamic SSH port forwarding was added to SSH clients it can safely be assumed the feature has been around for a while. The contents of this post was tested with a wide range of SSH clients, from Oracle Linux 8.6 to Debian 11, Ubuntu 22.04, and Windows 10 22H2. A similar feature exists for SSH clients on MacOS and Linux, and even on Windows's command-line SSH client as it's based on OpenSSH, too. after the session has already been established. One of the nice things in Putty is its ability to add port forwarding rules on the fly, e.g. Putty is still one of the most popular tools available to perform remote administration on Windows, despite the fact that recent Windows versions do provide an SSH client. For a very long time Windows did not provide a SSH client out of the box leading to a pleathora of 3rd party clients. As a Linux or Mac user you benefit from a very useful, built-in terminal and SSH client implementation that’s mostly identical across all Unix-like systems.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |