void badCertificateCallback=(bool callback(X509Certificate cert, String host, int port))

Sets a callback that will decide whether to accept a secure connection with a server certificate that cannot be authenticated by any of our trusted root certificates.

When an secure HTTP request if made, using this HttpClient, and the server returns a server certificate that cannot be authenticated, the callback is called asynchronously with the X509Certificate object and the server's hostname and port. If the value of badCertificateCallback is null, the bad certificate is rejected, as if the callback returned false

If the callback returns true, the secure connection is accepted and the Future<HttpClientRequest> that was returned from the call making the request completes with a valid HttpRequest object. If the callback returns false, the Future<HttpClientRequest> completes with an exception.

If a bad certificate is received on a connection attempt, the library calls the function that was the value of badCertificateCallback at the time the request is made, even if the value of badCertificateCallback has changed since then.

Source

set badCertificateCallback(bool callback(X509Certificate cert,
                                         String host,
                                         int port));