You can use any SSH (Secure SHell) server such as OpenSSH (http://openssh.org) as a sharing gateway. You just need to make sure that the "port forwarding" feature of the server is enabled. For an SSH server, "port forwarding" is one of the basic features. So, if you have an SSH server, you shouldn't have any problem finding and activating the feature. (In most SSH servers, "port forwarding" is enabled by default.)