The Tunnels panel allows you to configure tunnelling of arbitrary connection types through an SSH connection.
Port forwarding allows you to tunnel other types of network connection down an SSH session. See section 3.5 for a general discussion of port forwarding and how it works.
The port forwarding section in the Tunnels panel shows a list of all the port forwardings that PuTTY will try to set up when it connects to the server. By default no port forwardings are set up, so this list is empty.
To add a port forwarding:
popserver.example.com:110
.
To remove a port forwarding, simply select its details in the list box, and click the ‘Remove’ button.
In the ‘Source port’ box, you can also optionally enter an IP address to listen on, by specifying (for instance) 127.0.0.5:79
. See section 3.5 for more information on how this works and its restrictions.
In place of port numbers, you can enter service names, if they are known to the local system. For instance, in the ‘Destination’ box, you could enter popserver.example.com:pop3
.
You can modify the currently active set of port forwardings in mid-session using ‘Change Settings’ (see section 3.1.3.4). If you delete a local or dynamic port forwarding in mid-session, PuTTY will stop listening for connections on that port, so it can be re-used by another program. If you delete a remote port forwarding, note that:
If you ask to delete a remote port forwarding and PuTTY cannot make the server actually stop listening on the port, it will instead just start refusing incoming connections on that port. Therefore, although the port cannot be reused by another program, you can at least be reasonably sure that server-side programs can no longer access the service at your end of the port forwarding.
If you delete a forwarding, any existing connections established using that forwarding remain open. Similarly, changes to global settings such as ‘Local ports accept connections from other hosts’ only take effect on new forwardings.
If the connection you are forwarding over SSH is itself a second SSH connection made by another copy of PuTTY, you might find the ‘logical host name’ configuration option useful to warn PuTTY of which host key it should be expecting. See section 4.13.5 for details of this.