specify interface to send out multicast packets

mcast_iface.coffee

os =require 'os'
dgram = require 'dgram'

test_send = (ifaddr)->
  MDNS_PORT = 5354 # OSX refuses app to use port 5353 
  MDNS_ADDRESS = "224.0.0.251"
  s = dgram.createSocket('udp4')
  ver = Number(process.versions.node.split('.')[1])
  if ver==10
    s.bind MDNS_PORT, ifaddr, ->
      s.addMembership( MDNS_ADDRESS)
      s.send new Buffer('abcd'), 0, 4, MDNS_PORT, MDNS_ADDRESS, (err,bytes)->
        console.log 'send err=', err
        console.log 'send bytes=', bytes
  else if ver==8
    s.bind MDNS_PORT, ifaddr
    s.addMembership( MDNS_ADDRESS)
    s.send new Buffer('abcd'), 0, 4, MDNS_PORT, MDNS_ADDRESS, (err,bytes)->
      console.log 'send err=', err                                                              
      console.log 'send bytes=', bytes
  else
    console.log "unsupported node version:", ver
    
valid_interfaces = ->
  vifs=[]
  for ifnm, ifaddrs of os.networkInterfaces()
    for a in ifaddrs
       continue if a.family is 'IPv6' or a.internal is true
       vifs.push name:ifnm, address:a.address
  vifs

process.stdin.resume()
process.stdin.setEncoding("ascii")
vifs = valid_interfaces()
console.log vifs
console.log 'please select the interface:'
process.stdin.on 'data', (input) ->
  input = input.replace('\n', '')
  if input not in (iface.name for iface in vifs)
    console.log "#{input} is not a valid interface"
    return
  for iface in vifs
    if input == iface.name
      test_send iface.address
      break
  

    

tested successfully on windows XP and OSX

not work in node v0.10.

dgram.js:382
    throw new errnoException(process._errno, 'addMembership');
          ^
Error: addMembership EBADF
    at new errnoException (dgram.js:440:11)
    at Socket.addMembership (dgram.js:382:11)
    at test_send (/Users/timwu/Dropbox/programming/coffee/multicast/mcast_iface.coffee:15:7)
    at ReadStream.<anonymous> (/Users/timwu/Dropbox/programming/coffee/multicast/mcast_iface.coffee:71:9)

nodejs/node-v0.x-archive#4944

fixed!