iOS Programming: The Big Nerd Ranch Guide, Second Edition

For the More Curious: TXTRecords

While Bonjour does not allow a client and server to exchange information, a service published via Bonjour can include additional information that can be read by clients. For example, a printer could tell clients that it is in the third-floor library, or a workstation could display the rules for using it. Every NSNetService has a TXT Record for this purpose.

You can create a TXT Record with an NSDictionary. This dictionary has some restrictions – its keys can only be NSStrings, and its values must be NSData objects that encapsulate an NSString or binary data. Once you have a valid dictionary, you pass it to the class method dataFromTXTRecordDictionary: of NSNetService and set it as an NSNetService’s TXTXRecordData ...