Bencode-RPC

Remote Procedure Call in OCaml, with B-encode and Lwt.

This library allows to communicate through the network (TCP) using a remote call abstraction. The data is serialized with Bencode.

Documentation is available here.

Install

You need OCaml>=4.00, and the libraries bencode, lwt and lwt.unix.

$ make
$ make install

License

Released under the BSD2 license. See LICENSE.

Modules

The library provides the following modules, packed in the module Bencode_rpc:

• NetTcp: management of TCP connections, and communication of Bencode objects through sockets
• RPCServer: RPC server implementation. Methods (functions from Bencode messages to lwt-wrapped Bencode replies, basically) can be registered under a name to the server.
• RPCClient: connects to a server via TCP, and then allows to call remote methods by their name (with a timeout) and get a future response.
• Broadcast: untested broadcasting algorithm for small networks.
• Lwt_queue: a message queue for Lwt, for internal use
• Signal: internal publish/subscribe implementation

Example

Simple "ping-pong" client-server exchange (can be found in tests/test1.ml with minor modifications).

open Bencode_rpc;;
module B = Bencode;;

(* create a server that listens on some random TCP port *)
let server =
  match RPCServer.create () with
  | Some s -> s
  | None -> failwith "could not start server"
;;

let port = RPCServer.port server;;

(* register a method "ping" on the server. That remote method
   will reply "pong" whenever it receives "ping". *)
RPCServer.register server "ping" (fun _addr_sender msg ->
  match msg with
  | B.String "ping" -> RPCServer.reply (B.String "pong")
  | _ -> RPCServer.error "error: expected \"ping\"");;

let (>>=) = Lwt.(>>=);;

Lwt_main.run (
  (* create a client that tries to connect on the local port of the server *)
  RPCClient.local port
  >>= function
  | None -> failwith "could not connect to server port"
  | Some client ->

  (* call the remote method "ping" with the message "ping" (in Bencode)
     and a timeout of 2 seconds. *)
  RPCClient.call ~timeout:2. client "ping" (B.String "ping")
  >>= function
    | RPCClient.Reply (B.String "pong") ->
      Lwt_io.printl "success!"
    | RPCClient.Reply _ -> failwith "client: bad response"
    | RPCClient.Error msg -> failwith ("client: got error " ^ msg)
    | RPCClient.NoReply -> failwith "client: timeout"
);;