A pointer to an opaque I/O connection object.
- iOS 5.0+
- macOS 10.2+
- tvOS 9.0+
- watchOS 2.0+
The I/O connection object refers to data that identifies a connection. The connection data is opaque to Secure Transport; you can set it to any value that your application can use in the callback functions
SSLWrite to uniquely identify the connection, such as a socket or endpoint. Use the
SSLSet function to assign a value to the connection object.