Shell Tunnel

Shell Tunnel is a wonderful program that comes with -L and -R options in ssh(1) for normal shell. With this admirable feature, it uses a client program and a server program that are essentially the same program with different options. When you launch the client program from your computer, it automatically launches an ssh to your server. You can also easily modify the launched program using the --shell options. And once you launch the program with --server options on your server, it opens up the shell, and then you can do whatever you want with your port redirected.

In technical terms, the server and client are designed to detect some special formats in normal flow that are threated like data from sockets or control information, as you will see in the note.txt file. The program is typically used as a compilation farm to test client programs without installing the server one. This is especially useful when you can’t install the server or when the server is too heavy, like a proprietary database.

Originally written in Perl and later ported to C with additional features like pseudo terminals, the program also comes with a classifier utility that distinguishes single output/error streams. This utility is perfect for scripting and supporting multiple streams, even when only a single stream is available. Please note that the shtunnel and shserver Perl files are not compatible with the C version.

The latest release of Shell Tunnel comes with some significant changes. For starters, the program no longer passes a log file descriptor to a child process. Secondly, the tty is now set correctly, and the HTML output in the classifier now correctly closes span tags. Lastly, the full HTML output in the classifier has been revamped to include colors in style for additional streams based on terminal colors. Overall, Shell Tunnel is an indispensable software solution that makes life a lot easier for developers looking to test their programs on remote servers.