JSch is a pure Java implementation of SSH2.
JSch allows you to connect to an sshd server and use port forwarding, X11 forwarding, file transfer, etc., and you can integrate its functionality into your own Java programs. JSch is licensed under BSD style license.
Originally, our motivation to develop this stuff is to allow users of our pure java X servers, WiredX, to enjoy secure X sessions. So, our efforts had mostly targeted to implement the SSH2 protocol for X11 forwarding. Of course, however, we are now also interested in adding other functionality like port forward, file transfer, terminal emulation, etc.
Needless to say, SSH provides support for secure remote login, secure file transfer, and secure TCP/IP and X11 forwarding. It can automatically encrypt, authenticate, and compress transmitted data. The SSH protocol is available in two incompatible varieties: SSH1 and SSH2. SSH2 was invented to avoid the patent issues regarding RSA (RSA patent has expired), and to fix some data integrity problem that SSH1 has, and for a number of other technical reasons. SSH2 protocol has been standardized on IETF Secure Shell working group and drafts related to SSH2 protocol are available on the web. In developing JSch, we are now referring to following documents: