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I have a client-server system implemented in C#, and the client and server exchange .Net objects via serialization / deserialization and communicating via TCP/IP. This runs on a local network, it is not web-based or Internet-based.

Now I want to include Android clients connected by wifi. Again, this is local network only, not via the Internet and not web-based. The Android programming will be in Java. (I am aware of Mono for Android, but prefer not to get into that now.)

Is there some fairly simple way to implement object to object interchange between Java and .Net objects, provided, of course, that they are compatible?

I've looked a bit at JSON (Jackson on the Java end and Json.Net on the .Net end), and I'm guessing it can probably be done, but only with major efforts on remapping things at each end as soon as the objects become fairly complicated.

Any other suggestions? JSON-based or otherwise?

PS. My question is somewhat related to this one Mapping tool for converting Java's JSON to/from C#, but it never got a suitable answer, perhaps due to insufficient info in the question. Also, I don't care whether I end up using a JSON-based transport or XML or something else.

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RenniePet
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    Check out these question: http://stackoverflow.com/questions/2001405/strategy-for-cross-language-java-and-c-object-serialization and http://stackoverflow.com/questions/1303792/net-to-java-serialization-deserialization-compatibility – default locale Jul 23 '13 at 12:18
  • @defaultlocale: Thanks. I was completely unaware of Protocol Buffers. I've played around with it a bit in C#, and am pretty sure that's what I'm going to use. Please post that as an answer and I'll accept it. – RenniePet Jul 24 '13 at 01:32

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I would suggest either JSON or XML (which is based on a .xsd file) because these are independent of their respective implementations (instead of something like an ObjectOutputStream in java).

The problem of having this format between the two components (client and server) is that they need to be at the same version. My best practice is to have one underlying definition of the format (i use xml with an xsd file which specifies how the xml has to look like), then use jaxb to generated java classes. That way you can (un)marshal from/to xml in the java part.

I am very sure a similar thing exists in the world of .NET.

JSON is smaller than xml in size, i find xml to be more readable.

f1sh
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SO user "default locale" should get the honor for this, but he/she has only answered via a comment. So just to make it very clear what my choice was I'll answer my own question.

I've decided to go with Google Protocol Buffers, which in my opinion has much better support for moving objects back and forth between Java and .Net than JSON. Because I have a lot of experience with C#, and a lot of existing C#-defined classes, I've selected Marc Gravell's protobuf-net program for the .Net end, and Google's own support for the Android end (no - see edit). This implies that I'm defining the objects in C#, not in .proto files - protobuf-net generates the .proto files from which I then generate the Java code.

Incidentally, as the transport mechanism I'm using a little-known program called naga on the Android end. http://code.google.com/p/naga/ Naga seems to work fine, and is well-documented and has sample programs, and should be better known in my opinion.

EDIT:

OK, I've got it working now to my satisfaction. Here's what I'm using:

Google Protocol buffers as the interchange format: https://developers.google.com/protocol-buffers/

Marc Gravell's protobuf-net at the C# end: http://code.google.com/p/protobuf-net/

A program called called protostuff at the Java end: http://code.google.com/p/protostuff/

(I prefer protostuff to the official Google Java implementation of protocol buffers due to Google's implementation being based on the Java objects being immutable.)

Actually, I'm not using pure protocol buffers as the interchange format - I prefix the data with the name of the (outermost) class being transmitted. This makes the data self-identifying for deserializing at the other end.

RenniePet
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You can also try wox (https://github.com/codelion/wox), it is a cross platform serialization library for Java and C# based on XML.

codelion
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