SSLEngine only supports TLS 1.1 and 1.2 on android API lvl 20 or greater.
enableTLSProtocolOnOlderVersionsOfAndroid(Context context, String protocol)
lets the user set a protocol (ex: "TLSv1.2") and update the SSLEngine that AndroidAsync is using to permit older versions of Android to use TLS.
I tested it on API lvl 16 at the lowest, I am unsure if it works for versions below that.