protected Socket createSocket() {
        return new Socket();
    }
Returns a new unconnected socket.
<p>
Implementation notice for subclasses: This function is called by the
constructors which open the connection immediately. In these cases the
subclass is not yet initialized, therefore subclasses overriding this
function shouldn't use those constructors.
src/test/java/de/gessnerfl/fakesmtp/smtp/client/SMTPClient.java