zerorpc-node
============

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ZeroRPC is a communication layer for distributed systems. zerorpc-node is a port of the original [ZeroRPC](https://github.com/0rpc/zerorpc-python) for node.js. We have full client and server support for version 3 of the protocol, and clients/servers written in the Python version can communicate transparently with those written in node.js. This project is in alpha.

To install the package:

Make sure you have [ZeroMQ](https://github.com/zeromq/libzmq) installed.

Then:

```bash
npm install zerorpc
```

If you get the error `Package libzmq was not found` after making sure ZeroMQ is installed, take a look at [the fix for zeromq.node](https://github.com/JustinTulloss/zeromq.node/issues/55). If you get the error `Unable to load shared library <<path to zeromq.node>>/binding.node`, [make sure you run ldconfig](https://github.com/JustinTulloss/zeromq.node/issues/85). If that still doesn't work, check out [this ticket](https://github.com/JustinTulloss/zeromq.node/issues/92).

Servers
-------

To create a new server:

```js
var zerorpc = require("zerorpc");
var server = new zerorpc.Server(context [, heartbeat]);
```

The constructor takes in a context object with the functions to expose
over RPC. Only functions that do not have a leading underscore will be
exposed. Each exposed method must take in a callback as the last
argument. This callback is called as `callback(error, response, more)`
when there is a new update, where error is an error object or string,
response is the new update, and more is a boolean specifying whether new
updates will be available later. `error`, `response`, and `more` default
to falsy values, so e.g. simply calling `callback()` closes an open
stream, since `more` is false by default. Constructor also takes a
heartbeat parameter that specifies the interval that the server should
ping clinets to let them know it is active.

Events:

* `error` - When an error occurs.

Methods:

* `bind(endpoint)` - Binds the server to the specified ZeroMQ endpoint.
* `connect(endpoint)` - Connects the server to the specified ZeroMQ endpoint.
* `close()` - Closes the ZeroMQ socket.

Full example:

```js
var zerorpc = require("zerorpc");

var server = new zerorpc.Server({
    addMan: function(sentence, reply) {
        reply(null, sentence + ", man!");
    },

    add42: function(n, reply) {
        reply(null, n + 42);
    },

    iter: function(from, to, step, reply) {
        for(i=from; i<to; i+=step) {
            reply(null, i, true);
        }

        reply();
    }
});

server.bind("tcp://0.0.0.0:4242");

server.on("error", function(error) {
    console.error("RPC server error:", error);
});
```

Clients
-------

To create a new client:

```js
var zerorpc = require("zerorpc");
var client = new zerorpc.Client(options);
```

The constructor optionally takes in an options object. Allowable options:

* `timeout` (number) - Sets the number of seconds to wait for a response before considering the call timed out. Defaults to 30.
* `heartbeatInterval` (number) - Sets the number of miliseconds to send send heartbeats to connected servers. Defaults to 5000ms.

Events:

* `error` - When an error occurs.

Methods:

* `bind(endpoint)` - Binds the client to the specified ZeroMQ endpoint.
* `connect(endpoint)` - Connects the client to the specified ZeroMQ endpoint.
* `close()` - Closes the ZeroMQ socket.
* `invoke(method, arguments..., callback)` - Invokes a remote method.
  * `method` is the method name.
  * `arguments` are a list of arguments passed to the method, if there are no arguments then this argument is ommitted
  * `callback` is a method to call when there is an update. This callback is called as `callback(error, response, more)`, where error is an error object, response is the new update, and more is a boolean specifying whether new updates will be available later (i.e. whether the response is streaming).

Full example:

```js
var zerorpc = require("zerorpc");

var client = new zerorpc.Client();
client.connect("tcp://127.0.0.1:4242");

client.on("error", function(error) {
    console.error("RPC client error:", error);
});

client.invoke("iter", 10, 20, 2, function(error, res, more) {
    if(error) {
        console.error(error);
    } else {
        console.log("UPDATE:", res);
    }

    if(!more) {
        console.log("Done.");
    }
});
```