[B<-dtls1>]
[B<-dtls1_2>]
[B<-listen>]
+[B<-async>]
[B<-no_ssl3>]
[B<-no_tls1>]
[B<-no_dhe>]
HelloVerifyRequest. If a ClientHello with a cookie is received then s_server
will connect to that peer and complete the handshake.
+=item B<-async>
+
+switch on asynchronous mode. Cryptographic operations will be performed
+asynchronously. This will only have an effect if an asynchronous capable engine
+is also used via the B<-engine> option. For test purposes the dummy async engine
+(dasync) can be used (if available).
+
=item B<-bugs>
there are several known bug in SSL and TLS implementations. Adding this