Unit-tests for socket-based clients can be a pain to write. You need some kind of server for them to attach to, and a way to control and detect traffic going both ways. Writing such a server with sockets is reasonably straightforward but requires some nasty thread management. NIO is clearly a better approach, but a fair bit more work, and not worth repeating. SimpleServer provides a very basic NIO implementation, suitable for such testing.
The server is instantiated with one parameter, a callback listener. The simplest approach is to have the test class implement the listener interface, so:
SimpleServer server = new SimpleServer(this);
The listener will then receive callbacks as the server operates. Most test logic is likely to go in the dataRead method, invoked when the server receives data from a socket. The Responder can be used to check the data, close the connection from the server side, or send a reply. Other callbacks allow the test to verify that a connection has been made and that a reply has been sent.
