srop

SROP

Simple remote object protocol. Think smalltalk, erlang and 9p, not CORBA or SOAP.

Explicit goals of the protocol are:

• Simplicity
• Security
• Flexibility

The protocol is based on message passing where clients send arbitrary messages to objects on a server and the objects are able to reply with arbitrary messages. Specific applications may define how the objects it serves will respond to different application specific messages. There is a small set of messages the reference implementation defines that other implementations are encouraged to reuse.

Applications may define their own message types by simply selecting a unique 64 bit identifier for that message and defining the message format. There is no need for complex protocol negotiation, objects simply respond to messages they understand. If an object recieves a message it does not understand, it can reply with an 'UnknownMessage' response.

The allocation of new objects and their corresponding id on the server is an application detail. For example a message sent to the root object may trigger the allocation of a new object. Communicating new ids to the client is an application detail, but would generally be communicated via an application specific response message.

Object ids could be considered analagous to file descriptors in an operating system, where having an object id associated with a session implies permission to send that object messages. This means SROP makes capability based security quite simple to implement.

Example

Running the example

$ go run example/server/main.go 
  listening on 127.0.0.1:4444
  RootObject got a message: &example.MakeGreeter{Name:"bob"}
  I just greated a greeter with id: 1
  greeter 1 got a message: &example.Hello{From:"client"}
  client just said hello to me, saying hello back in one second.
  greeter 1 got a message: &srop.Clunk{}
  destroying myself.
  Greeter with id 1 clunked.
  RootObject clunked.

$ go run ./example/client/main.go
  Creating a new greeter named bob by contacting the bootstrap object...
  Saying hello to our new greeter...
  Got a reply from: bob
  destroying the greeter...
  closing the connection...

Talking to the example Greeter server from go

  client := srop.NewClient(c, srop.ClientOptions{})

  // The server root object responds to MakeGreeter messages by returning us a new object handle.
  reply, _ := client.Send(srop.BOOTSTRAP_OBJECT_ID, &example.MakeGreeter{Name: "bob"})

  greeterId := reply.(*srop.ObjectRef).Id

  // Sending hello to our newly created remote greeter results in a reply hello message.
  reply, _ = client.Send(greeterId, &example.Hello{From: "client"})

  fmt.Printf("greetings from: %s" reply.(*example.Hello).From)

  client.Close()

Specification

here

Implementations

• Go - The reference implementation in this repository.