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I'm looking for a very simple way to allow RPC between Java and C++ applications.

My system contains several Java modules and one C++ module. I have not too much different procedures to call (about 2-3 per module), and they will not change much (except some minor adaptations like adding a new procedure or changing one's prototype). I am writing all the modules so I can use whatever I want. Also, the modules are to be all executed on the same machine, except for one, but the possibility of executing some of them on another machine without to much harass (basically, just changing a configuration file) would be a plus.

All the modules, the machines and the networks used for this application are trusted but I don't want any security flaw on the RPC protocol and I want a minimal performance overhead, so the simpliest the RPC protocol is, the better. Also, each method called has one prototype only.

At the moment I'm trying to use RPC through TCP sockets, as I don't want to use RMI nor Unix primitives (no standard implementation on Java and no network capabilities). I have written a very simple RPC protocol: through a TCP frame you give the serialized name of the method called, followed by the serialized list of arguments. On the server side, it listens on an object and uses reflection to execute the method given. In case of error, the returned object is a DistantRPCError encapsulating the error.

The code is very simple (only about 100 loc) and can be used in a large variety of situations (I work with Streams, so I'm not even depending on Sockets). The problem I am facing is that I can not test my code statically (The simple initialization of a local test is longer than the tested code) and I can not really see how hard this would be to implement it in C++ (using JNI for serialization, I suppose).

So my question is: do you know of a different way of making RPC calls in both Java and C++ that is really simple (so no RMI) and can be trusted (I'm not looking for a shinny piece of technology, I want something standard and industry-proofed). Also, I have some limitations on the performances (the machine is a low-cost computer and I have a lot of cryptology to do locally). And as I said, the majority of the modules (except for one or two) are executed locally, so I'm also interested in IPC mechanisms (even if it would be nice to have only one RPC mechanism for all my modules).

I can give you my actual RPC code if you want, but as I said it is not even tested, so I am not sure it works at all.

Edit: I will probably use SOAP, as I don't see much interest in using an ORB for my specific problem. Thanks for the idea !

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I don't know if either one would meet your criteria for simplicity, but I'd say your two best bets are something old - CORBA - and something new - web services.

CORBA comes to mind because interoperation of distributed components written in different languages was part of its inspiration, but it's not simple. The marketplace has also voted against CORBA. I would say it hit its peak in the early to mid 90s and has declined since. I don't hear much about CORBA, for what it's worth.

Web services, especially if you eschew SOAP and go with REST, work over HTTP and are relatively simple. I don't see any advantage in developing and maintaining your own wire protocol. I'd use HTTP and stick with REST.

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CORBA seems the best option to me.
I don't know, using a component based approach seems a little bit overkill, and I don't know how a local HTTP server would work performance-wise (I can have up to 8 modules working together locally and making like 50 RPC per second); but thank you, I'll look into these approachs !
I don't see how doing RPC over sockets using a custom protocol is not component based. The words "component" and "module" seem interchangeable to me. If performance is an issue, you'll be worried more about all the network latency you're introducing than anything else.
You are right, this is close to a component-based approach, but if have multiple "modules" it is mostly for duplication: executing two different code having the same specification but different implementations in order to avoid errors in the implementation (if the two are different, then I do nothing and log an error). That is why I have to split my code between multiple executables (this and I also have some moderately trusted code I need to run in a sandboxed JVM).
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Just so you know, I finally choose to use MessagePack for all my RPC, the point is: it is very simple to use, open-source (with a small code base) and it works wonderfully.

The downsides are: there is no comments at all for the java lib, but as I said it is open source with a small code base and a simple architecture so there is no problem understanding how it works.

Also there is a lot of different developpement versions for the java libs (which can mean an unstable API, but I won't update the lib once the system will be finished, so it is not a problem) and I could not compile the C++ lib on windows (which is not really a problem for me, since I use it on Linux).

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Leo, I know this is rather old, but how did this decision work out for you? I'm looking to add RPC to a stand alone application written in Java so we can call tasks remotely but adding REST or SOAP or whatnot seems too cumbersome. This seems to be simple. Did it work out?
Hi, this decisions worked well for me, message pack has been great for the project. I'm not on the same project anymore and the codebase seems to have changed a bit, but if I had to chose a serialization algorithm again I would still go for it: it is simple and the codebase is small so you can easily adapt the code to your particular needs.

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