A simple TCP proxy and a few other pieces. The TCP proxy is embeddable in other Java applications. Two front ends are provided a CLI and a GUI. The TCP proxy was originally implemented after using a TCP proxy in tests so it is possible to do things not usually desirable such as dropping or delaying writes.
An alternative networking API is provided that wraps the Java standard library implementation. This was done to simplify unit testing. The opportunity was taken to clean up some of the rough edges around the socket API. It is focused on non-blocking I/O but does not differ significantly from the JSL.
A TCP proxy is not very original and there are many implementations. I inherited the code for one at work which wasn't very good. We also had three different versions of it lying around. I spent a morning replacing them with a cleaner, single implementation. I wasn't very happy with it though because it took the same approach to threading as the one it replaced. Spawn two threads for each proxied connection.
I decided to implement a proxy that used Java's NIO library using non-blocking I/O to allow multiple connections to be handled by the same threads.
There are eight separate modules. An I/O API module, an I/O implementation module, selector module, a proxy implementation module, a command line interface argument parsing module, a command line interface module, a graphical user interface module and an examples module.
The TCP proxy uses Java NIO. The socket reads and writes do not block, accepting new connections still block. A single thread is used to accepting connections, reading and writing data. Data read from a socket is placed on a queue that is consumed by the thread responsible for writing data. Since very small amounts of data can be returned by NIO reads, individual reads are batched before attempting to write them.
Module that provides an API for performing socket I/O. It is focused on providing non-blocking operations. It provides interfaces for classes responsible for performing network operations. It also provides some concrete classes for value objects used to configure sockets.
Module that provides an implementation of the tcProxy IO API module that delegates to the Java Standard Library.
Module that provides simple workers that can be stopped and restarted.
Module that provides a layer over the tcProxy IO API module to provide more friendly and common selector operations.
Module that implements a simple reverse proxy server. It uses non-blocking I/O, selectors and a limited number of threads to support multiple sockets.
Module that implements a reverse proxy server. It uses non-blocking I/O, selectors and a limited number of threads to support multiple sockets. It allows the data read to be processed and manipulated. Data can be dropped or delayed.
Module that provides a GUI frontend to the proxy server.
Module that provides a CLI frontend to the proxy server.
Module that supports parsing CLI arguments.
Module that provides examples of the other modules. It provides a HelloExample that shows how to use sockets from the I/O API. It provides an EchoServer that shows how to build on top of the selectors module. It provides the examples SimpleExample and BiDirectionalExampe to show the use of the proxy server.