anchor.diff:  %%  <dt>cacertfile</dt><dd>Optional. Path to file containing PEM encoded
   %%   CA certificates (trusted certificates used for verifying a peer
   %%   certificate).</dd>
  +%%  <dt>cert</dt><dd>Optional. The DER encoded users certificate. If this
  +%%   option is supplied it will override the certfile option.</dd>
   %%  <dt>certfile</dt><dd>Mandatory. Path to a file containing the user's
   %%   certificate.</dd>
   %%  <dt>ciphers</dt><dd>Optional. The cipher suites that should be supported.
  
positive.code: 	| {port, inet:port_number()}
  	| {raw, non_neg_integer(), non_neg_integer(),
  		non_neg_integer() | binary()}
  	| {verify, ssl:verify_type()}].
  -export_type([opts/0]).
  
  %% @doc Name of this transport, <em>ssl</em>.
  
negative.code: %%   certificate is considered valid).</dd>
  %%  <dt>ip</dt><dd>Interface to listen on. Listen on all interfaces
  %%   by default.</dd>
  %%  <dt>key</dt><dd>Optional. The DER encoded users private key. If this option
  %%   is supplied it will override the keyfile option.</dd>
  %%  <dt>keyfile</dt><dd>Optional. Path to the file containing the user's
  %%   private PEM encoded key.</dd>
  %%  <dt>next_protocols_advertised</dt><dd>Optional. Erlang R16B+ required.
  