• Open Menu Close Menu
  • Apple
  • Shopping Bag
  • Apple
  • Mac
  • iPad
  • iPhone
  • Watch
  • TV
  • Music
  • Support
  • Search apple.com
  • Shopping Bag

Lists

Open Menu Close Menu
  • Terms and Conditions
  • Lists hosted on this site
  • Email the Postmaster
  • Tips for posting to public mailing lists
Re: broadcast address of a network interface
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: broadcast address of a network interface


  • Subject: Re: broadcast address of a network interface
  • From: Jens Alfke <email@hidden>
  • Date: Mon, 9 Feb 2009 08:47:28 -0800


On Feb 9, 2009, at 8:37 AM, Joel Reymont wrote:

I would like to broadcast audio from the iPhone to other iPhones or Macs on a subnet.

This is often done using multiple TCP sockets instead of multicast. The advantage is that, since TCP is reliable, you don't have to worry about dealing with dropped packets (which are rare on Ethernet, but common in busy wireless networks). It also works transparently outside the local subnet.


It may seem like a waste of bandwidth, but audio doesn't use that much bandwidth anyway, and it turns out that multicast has bad effects on 802.11 (IIRC, the base station has to drop the network down to low speed temporarily while it sends a multicast packet). I've had a few conversations with Bonjour experts about this in the past, and at least one of them recommended just going to TCP for streaming.

If I go with multicast, how do I programmatically find a proper multicast address?

There's a limited name- [number-]space of them, so they're assigned manually by the IETF. If you search around, there's an RFC that's a registry of registered multicast addresses; you look for an unused link-local one and request for it to be assigned to you, using the email address given in the RFC. (Or if you don't think your app will be widely used, you can just pick a free one and use it as a squatter; but I don't think the registration process is too onerous.)


—Jens

Attachment: smime.p7s
Description: S/MIME cryptographic signature

 _______________________________________________
Do not post admin requests to the list. They will be ignored.
Macnetworkprog mailing list      (email@hidden)
Help/Unsubscribe/Update your Subscription:

This email sent to email@hidden

  • Follow-Ups:
    • Re: broadcast address of a network interface
      • From: Joel Reymont <email@hidden>
References: 
 >broadcast address of a network interface (From: Joel Reymont <email@hidden>)
 >Re: broadcast address of a network interface (From: Jens Alfke <email@hidden>)
 >Re: broadcast address of a network interface (From: Joel Reymont <email@hidden>)

  • Prev by Date: Re: broadcast address of a network interface
  • Next by Date: Re: broadcast address of a network interface
  • Previous by thread: Re: broadcast address of a network interface
  • Next by thread: Re: broadcast address of a network interface
  • Index(es):
    • Date
    • Thread