socket-events

Minimal RPC with event emitters

Compatible with NodeJS 6.0.0+

const se = require('socket-events');
 
// emit JSON events using any writable stream
const emit = se.writer(socket);
 
emit('foo', {hello: 'world'}); // emits '22;foo;{"hello":"world"};'
emit('bar');                   // emits '4;bar;'
 
// handle the events using any readable stream
const events = se.reader(socket, {
  foo: (data) => console.log('foo:', data),
  bar: () => console.log('bar'),
  '*': (name, data) => console.log({name, data}),
});
 
// bring your own event emitter (optional)
const EventEmitter = require('events');
const events = new EventEmitter();
se.reader(socket, events);
 
// use the encoder and decoder directly
const decode = se.decoder(events);
socket.on('data', decode);
socket.write(se.encode('foo', {hello: 'world'}));

Sockets are duplex streams, which means you can use both se.reader and se.writer on the same socket for bi-directional events.

The se.writer and se.reader functions work with any stream, not just sockets.

The decoder avoids parsing the event body if an event has no listeners.

 

Event emitters

The se.reader function can be passed any object with an emit method like this:

• emit(name: string, arg1: any, arg2: any) : any

The se.events function returns a custom EventEmitter object that is highly optimized for the minimal use case. There is no support for one-time listeners, addListener or removeListener events, or error events that throw when no listeners exist. You should provide se.reader with an instance of node's built-in EventEmitter class for those features.

// add listeners via the constructor
const ee = se.events({
  foo: console.log, // values can be functions
  bar: [],          // or arrays of functions
});
 
// listen to all events
ee.on('*', (name, data) => {});
 
// listen to one event
const listener = ee.on('foo', (data) => {});
 
// emit an event manually
ee.emit('foo', 123);
 
// remove a listener
ee.off('foo', listener);
 
// remove all listeners of an event
ee.clear('foo');
 
// remove all listeners of all events
ee.clear();

 

Event serialization

Socket events have a length, an event name, and an event body.

22;foo;{"hello":"world"};

The leading number indicates the number of bytes that come after its semi-colon.

The event name must not contain semi-colons or be empty.

The event body must be JSON-compliant, unless it's omitted.

4;bar;  // an event with no body

 

encode and decoder

The encode and decoder functions are used internally and in tests.

const msg = se.encode('foo', 1); // => '6;foo;1;'
se.decoder({
  foo(data) {
    console.log(data); // => 1
  }
})(msg);

 

Install

npm install socket-events

License

MIT