The data is sent once and is not sent again if a transmission error occurred.
- iOS 3.0–7.0Deprecated
- macOS 10.8–10.10Deprecated
- tvOS 9.0–9.0Deprecated
- watchOS 2.0–2.0Deprecated
Data transmitted unreliably may be received out of order by recipients. Use this for small packets of data that must arrive quickly to be useful to the recipient.