The following is a list of possible keys that you can use, and the possible values to use

Key	Possible Values
NSStream.SocketSecurityLevelKey	The security level used by the SSL/TLS stack. It should be one of: NSStream.SocketSecurityLevelNone: No security level set for the stream. NSStream.SocketSecurityLevelSslV2: Use SSLv2 on the stream. NSStream.SocketSecurityLevelSslV3: Use SSLv3 on the stream. NSStream.SocketSecurityLevelTlsV1: Use TLSv1 on the stream. NSStream.SocketSecurityLevelNegotiatedSsl: Use the highest possible security protocol that can be negotiated on the stream.
NSStream.SOCKSProxyConfigurationKey	Set to a dictionary of configuration information for a SOCKS proxy. The list of possible values in this dictionary include: NSStream.SocksProxyHostKey: NSString containing the SOCKS proxy host name. NSStream.SocksProxyPortKey: NSNumber containing the SOCKS proxy host port. NSStream.SocksProxyVersionKey: The SOCKS proxy server version, use NSStream.SocksProxyVersion4 or NSStream.SocksProxyVersion5. NSStream.SocksProxyUserKey: NSString containing the SOCKS proxy user name. NSStream.SocksProxyPasswordKey: NSString containing the SOCKS proxy password.
NSStream.DataWrittenToMemoryStreamKey	Value is the NSData that is collecting data on the stream (get only).
NSStream.FileCurrentOffsetKey	NSNumber containing the position on the stream.
NSStream.NetworkServiceType	Type of service that the stream is providing, one of: NSStream.NetworkServiceTypeBackground: Background data. NSStream.NetworkServiceTypeVideo: Video data. NSStream.NetworkServiceTypeVoice: Voice service. NSStream.NetworkServiceTypeVoIP: Voice Over IP.