The Tunnel Library is a Java library for doing stream based I/O in Java over different kinds of transports. The design philosophy behind the Tunnel Library is to provide the developer with plain Java Socket and ServerSocket instances so that 1) the developer does not have to learn a new or complicated API to use the Tunnel Library, and 2) the developer can directly reuse any existing code or third-party libraries based on Java sockets without any modifications.

The HTTP tunnel supports Java Socket based I/O transparently over HTTP in all these situations, doing all the hard work for you and letting you concentrate on developing the core of your application. The HTTP tunnel:

• is extremely fast (it can easily handle 100MB/s)
• supports a large number of tunnels to a single server
• supports both the http and https protocols
• supports http proxies
• supports basic/digest/ntlm authentication
• supports basic/digest/ntlm proxy authorization
• is compatible with Apache 2.2 mod_proxy or mod_jk (ajp required, MPM-worker recommended)
• runs on any Servlet 2.4 compatible servlet container
• has many parameters to tune the tunnel to specific use cases

The Multiplexer acts both as a TunnelClient and TunnelServer and multiplexes many connections over a single Java Socket (and thus also over another tunnel). Since the multiplexer acts as a TunnelServer it also accepts connections, allowing connections to be made both ways even in environments with NAT. The Multiplexer:

• is extremely fast
• supports up to 64K connections per underlying connection
• shares bandwidth fairly between all the connections and saves on connection setup time
• allows the server side of the underlying connection to make connections back to the client
• is very useful when combined with the HTTP tunnel, allowing transparent bidirectional setup of connections

The multiplexed RMI Socket Factories combine the power of the Multiplexer with RMI. This allows you to use the RMI framework over a single underlying connection. Together with the HTTP tunnel this allows you to use bidirectional RMI over the internet, without having to worry about firewalls, HTTP proxies, or NAT routers. Since the RMI connections are multiplexed, setup time for new connections is minimal and the bandwidth sharing of the Multiplexer guarantees smoother operation than plain RMI. Using the Multiplexed RMI Socket Factories you can:

• look up and reference remote objects on the RMI server
• export remote interfaces from the client to the server, and let the server call methods of these interfaces
• replace complicated stateless web service oriented protocols with RMI, even when faced with firewalls, NAT routers and proxies

The Tunnel Library contains a port forwarding utility which can be used to tunnel any TCP based applications, such as SSH, database connections, etc. In combination with the HTTP tunnel using the https protocol, it is an easy way to tunnel arbitrary TCP connections securely over HTTP.

The tunnel library also contains TunnelClients and TunnelServers to add various cababilities to other tunnels.

• SSL tunnel: add an SSL encryption layer to any tunnel (e.g., an HTTP tunnel)
• Zlib tunnel: add compression to any tunnel