Polytalk is my latest open source project. I developed it out of the need to communicate with a legacy system running PHP while writing code in Ruby and Node.js to leverage the existing business logic.
The amazing thing with Polytalk is you don't need to write any extra APIs or write any additional code. All that's needed is the server which is a long running process that exposes classes to the client via TCP.
Here is a quick overview of what Polytalk taken from the project's page:
Polytalk is a simple protocol which allows communication between different languages via TCP. The protocol uses a simple JSON object to pass back and forth request and response information from the server and client.
Polytalk currently supports Ruby, Node.js and PHP. Each language module consists of a server and client that both follow the exact same API so implementation is simple. Installation of all the modules is equally as simple, utilizing the popular package managers for each language.
Polytalk is plug and play meaning you don't have to do any extra coding to expose your methods from your existing code base. This is great for legacy code or teams of polyglot developers.