These are various tutorials/how-tos, etc, available on the web, produced by the iOS development community. I plan on updating this post as/when I find more resources. Please get in contact if you have any resources you’d like to contribute to this list.

NSHipster on Multipeer Connectivity

You will find a great introduction to the whole Multipeer Connectivity framework on NSHipster. If you haven’t already, go read it, then come back here. Future posts I write on this topic will largely assume that you are familiar with the contents of the NSHipster article.

As of writing, there are a couple of issues with the posted NSHipster article.

First of all, when advertising a service, make sure to keep a strong reference to the MCNearbyServiceAdvertiser (e.g. in a property), otherwise when the object goes out of scope it will be deallocated (and hence advertising will stop):

MCNearbyServiceAdvertiser *advertiser =
    [[MCNearbyServiceAdvertiser alloc] initWithPeer:localPeerID
advertiser.delegate = self;
[advertiser startAdvertisingPeer];
self.advertiser = advertiser; // important! keep a strong reference!

Make sure, of course, to nil out your reference to the advertiser when you no longer need it!

The second issue is an actual bug. When browsing for nearby services, you have two options:

  1. Manually create a browser via the MCNearbyServiceBrowser class, and manage the UI yourself.
  2. Use the built-in MCBrowserViewController to handle both UI and browsing.

The supplied example combines the two - first create a browser object, then pass it to the browser view controller. This is possible, but when doing so, you should not manually invoke [browser startBrowsingForPeers] - the browser view controller does this automatically for you. Additionally, the browser view controller becomes the delegate for the browser.

So, the example code should be:

MCNearbyServiceBrowser *browser =
    [[MCNearbyServiceBrowser alloc] initWithPeer:localPeerID

MCBrowserViewController *browserViewController =
    [[MCBrowserViewController alloc] initWithBrowser:browser
browserViewController.delegate = self;
[self presentViewController:browserViewController animated:YES completion:nil];

Unless you need the browser object for another reason, though, it is simpler to just let the browser view controller create a browser itself:

// use the built-in browser view controller to connect to peers
MCBrowserViewController *browserViewController =
    [[MCBrowserViewController alloc] initWithServiceType:XXServiceType
browserViewController.delegate = self;
[self presentViewController:browserViewController animated:YES completion:nil];

Stack Overflow

This is a great place to get help, as well as help others. See questions tagged multipeer-connectivity.

Other Blogs

Besides NSHipster, I haven’t found many tutorials online about the Multipeer framework. Here is a sampling of what I have found so far:

Please feel free to let me know of any notable exceptions to the list above!

Demo projects on GitHub

Several people have developed demo projects showing how to approach writing multipeer code. A few examples are:

  • Easy Cards
  • MCSessionP2P demonstrates auto browsing/connecting. It works well with only 2 peers, but with a larger number of peers it is extremely unreliable. Auto-connecting peers is a problematic area and non-trivial to implement and I hope to discuss it further in a later post.