@param engine the server-side engine
@param protocols The list of client-supplied protocols
@return The function's result is an application protocol name, or {@code null} to indicate
that none of the advertised names are acceptable. If the return value is an empty
{@link string} then application protocol indications will not be used. If the return value
is {@code null} (no value chosen) or is a value that was not advertised by the peer, a
"no_application_protocol" alert will be sent to the peer and the connection will be
terminated.
Selects the appropriate ALPN protocol.
@param engine the server-side engine @param protocols The list of client-supplied protocols @return The function's result is an application protocol name, or {@code null} to indicate that none of the advertised names are acceptable. If the return value is an empty {@link string} then application protocol indications will not be used. If the return value is {@code null} (no value chosen) or is a value that was not advertised by the peer, a "no_application_protocol" alert will be sent to the peer and the connection will be terminated.