Udp Responder

This library lets you broadcast and listen to messages on a network through UDP.

It can validate a message was sent untampered at a certain time by using SHA256 hashing.

The UdpResponder class can take the following options

Property	Description	Type	Required	Default
multicast_addr	The address the UDP command receiver will listen on	string	false	224.1.1.1
port	The port the UDP command receiver will listen on	number	false	6811
secret	Specify the sha256 signature secret used to sign messages	string	false	CHANGEME
ttl	If using secure the time until a message expires	integer	false	5000

Properties and Methods

The UdpResponder class exposes the following methods and properties.

UdpResponder::on(event:string, fn:function)

Add an event listener. The following events can occur.

opened

udpResponder.on('opened', function () {
  console.log('The sender and listener have been opened')
})

closed

udpResponder.on('closed', function () {
  console.log('The sender and listener have been closed')
})

message

When a message is received it will have a command, possibly some data and information about the sender.

Messages received have their signature validated before being emitted.

The sender is "Remote address information" provided as rinfo from the node API. https://nodejs.org/api/dgram.html#dgram_event_message

udpResponder.on('message', function (cmd, data, sender) {
  console.log(`A new ${cmd} message has been received of:`, data)
})

rejected

See the rejection reasons section below for a list of possible rejection reasons.

Messages rejected have not had a signature validated, and also may not be in any form of readable format.

udpResponder.on('rejected', function (reason, message, sender) {
  console.log(`A message was rejected occured:`, reason, cmd)
})

UdpResponder::open()

Start listening for messages on the network

UdpResponder::close()

Stop listening for messages on the network

UdpResponder::broadcast(cmd:string, data:any)

Broadcast a message over the network. You must specify a command but data is optional.

Rejection Reasons

Rejections are returned as an instance of UdpResponderRejection.

Code	Direction	Description
INVALID_FORMAT	Incoming	Message received but could not be parsed as it was not in the correct format
INVALID_SIGNATURE	Incoming	Message received but had invalid signature.
EXPIRED	Incoming	Message received but expired ? milliseconds ago.
INVALID_DATA_TYPE	Incoming	Message received with invalid ? content and could not be parsed.
UNKNOWN_DATA_TYPE	Incoming	Message received but the data type of ? is unimplemented.

Example

const UdpResponder = require('ec-udp-responder')

const udpResponder = new UdpResponder({
  secret: 'abcdefg'
})

udpResponder.on('opened', async function () {
  udpResponder.broadcast('EXAMPLE-HELLO-COMMAND', {
    name: 'Joe Bloggs',
    hobbies: ['running', 'cycling', 'singing']
  })
})

udpResponder.on('message', async function (msg, sender) {
  if (msg.command === 'EXAMPLE-HELLO-COMMAND') {
    udpResponder.broadcast('EXAMPLE-WELCOME-COMMAND', `A warm welcome to ${msg.name}`)
  }
})

udpResponder.open()

// You can stop everything by calling close
// udpResponder.close()