NSStream defines these string constants as keys for accessing stream properties using property(for and setting properties with set:
SDKs
Framework
struct PropertyKey
static let dataValue is an NSData instance containing the data written to a memory stream.
static let fileValue is an NSNumber object containing the current absolute offset of the stream.
static let networkThe type of service for the stream. Providing the service type allows the system to properly handle certain attributes of the stream, including routing and suspension behavior. Most streams do not need to set this property. See Stream Service Types for a list of possible values.
static let socksValue is an NSDictionary object containing SOCKS proxy configuration information.