Bonjour over Bluetooth on iOS 5 and Later

Q:  After adopting the iOS 5 SDK my app no longer sees Bonjour services over Bluetooth. What's going on here?

A: When Bonjour over Bluetooth support was added in iOS 3.0, the default policy was that it should be enabled for all apps. That is, a Bonjour app would operate over Bluetooth unless it explicitly opted out of that behaviour.

This policy changed in iOS 5.0. The new policy is that a Bonjour app must explicitly opt in to Bluetooth support. This change was made to reduce interference with Wi-Fi. To ensure binary compatibility, this change is only enabled for apps that link with the iOS 5.0 SDK (or later). This explains why your previous app binary continues to see Bonjour services over Bluetooth, but your latest binary, built with a modern SDK, does not.

iOS 7 introduced a new NSNetService property, includesPeerToPeer, that you can set to explicitly enable registration and discovery over Bluetooth. If your app runs on iOS 7 and later, you can simply set that property and you're done.

If your app runs on iOS 5 or 6 and you want to reenable Bonjour over Bluetooth, you must switch to using the low-level DNS-SD API (<dns_sd.h>). For an example of how to integrate the DNS-SD API into a Cocoa application, take a look at Sample Code 'DNSSDObjects'.

Once you've adopted the DNS-SD API, you can set the interfaceIndex parameter to explicitly control the interfaces over which it operates. The standard value for this parameter, kDNSServiceInterfaceIndexAny, yields the default policy as explained above. You can modify this by passing in the kDNSServiceFlagsIncludeP2P flag, as shown in Table 1. Alternatively, you can browse for services over Bluetooth, and only over Bluetooth, by passing kDNSServiceInterfaceIndexP2P to the interfaceIndex parameter.

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