What is the difference between Java RMI and RPC?

Question

RPC is C based, and as such it has structured programming semantics, on the other side, RMI is a Java based technology and it's object oriented.

With RPC you can just call remote functions exported into a server, in RMI you can have references to remote objects and invoke their methods, and also pass and return more remote object references that can be distributed among many JVM instances, so it's much more powerful.

RMI stands out when the need to develop something more complex than a pure client-server architecture arises. It's very easy to spread out objects over a network enabling all the clients to communicate without having to stablish individual connections explicitly.

The main difference between RPC and RMI is that RMI involves objects. Instead of calling procedures remotely by use of a proxy function, we instead use a proxy object.

There is greater transparency with RMI, namely due the exploitation of objects, references, inheritance, polymorphism, and exceptions as the technology is integrated into the language.

RMI is also more advanced than RPC, allowing for dynamic invocation, where interfaces can change at runtime, and object adaption, which provides an additional layer of abstraction.

1. Approach:

RMI uses an object-oriented paradigm where the user needs to know the object and the method of the object he needs to invoke.

RPC doesn't deal with objects. Rather, it calls specific subroutines that are already established.

2. Working:

With RPC, you get a procedure call that looks pretty much like a local call. RPC handles the complexities involved with passing the call from local to the remote computer.

RMI does the very same thing, but RMI passes a reference to the object and the method that is being called.

RMI = RPC + Object-orientation

3. Better one:

RMI is a better approach compared to RPC, especially with larger programs as it provides a cleaner code that is easier to identify if something goes wrong.

4. System Examples:

RPC Systems: SUN RPC, DCE RPC

RMI Systems: Java RMI, CORBA, Microsoft DCOM/COM+, SOAP(Simple Object Access Protocol)

Remote Procedure Call (RPC) is a inter process communication which allows calling a function in another process residing in local or remote machine.

Remote method invocation (RMI) is an API, which implements RPC in java with support of object oriented paradigms.

1. You can think of invoking RPC is like calling a C procedure. RPC supports primitive data types where as RMI support method parameters/return types as java objects.

2. RMI is easy to program unlike RPC. You can think your business logic in terms of objects instead of a sequence of primitive data types.

3. RPC is language neutral unlike RMI, which is limited to java

4. RMI is little bit slower to RPC

Have a look at this article for RPC implementation in C

RMI or Remote Method Invokation is very similar to RPC or Remote Procedure call in that the client both send proxy objects (or stubs) to the server however the subtle difference is that client side RPC invokes FUNCTIONS through the proxy function and RMI invokes METHODS through the proxy function. RMI is considered slightly superior as it is an object-oriented version of RPC.

From here.

For more information and examples, have a look here.

The only real difference between RPC and RMI is that there is objects involved in RMI: instead of invoking functions through a proxy function, we invoke methods through a proxy.

The difference between RMI and RPC is that:

• RMI as the name indicates Remote Method Invoking: it invokes a method or an object. And
• RPC it invokes a function.