I've created an open source TCP Client/Server project that is on
GitHub as well. The server runs on Windows and is implemented in C#. The server also includes a Windows Authentication protocol, however; any authentication method can easily be implemented. The project includes client APIs for Windows (C#), Android (Java), iOS/OSX (Objective-C). I have also created an object access protocol that supports serialization of server-side C# objects, supports remote method invocation, passing of objects and arrays, variable (Property) subscriptions as well as event notifications. Although I haven't open sourced the object access protocol, I would like to offer the protocol to any developers that are interested in trying out the API. I will offer a free redistribution license. Please contact me at my email address or goto my
website.