An exception thrown when connecting: "None of the specific endpoints where reachable"

[herme063]

Describe the bug

I get this exception when connecting to a 3rd party rabbitmq server:

RabbitMQ.Client.Exceptions.BrokerUnreachableException: None of the specified endpoints were reachable
 ---> System.InvalidOperationException: BUG FOUND - please report this exception (with stacktrace) here: https://github.com/rabbitmq/rabbitmq-dotnet-client/issues
   at RabbitMQ.Client.EndpointResolverExtensions.SelectOneAsync[T](IEndpointResolver resolver, Func`3 selector, CancellationToken cancellationToken)
   at RabbitMQ.Client.Framing.AutorecoveringConnection.CreateAsync(ConnectionConfig config, IEndpointResolver endpoints, CancellationToken cancellationToken)
   at RabbitMQ.Client.ConnectionFactory.CreateConnectionAsync(IEndpointResolver endpointResolver, String clientProvidedName, CancellationToken cancellationToken)
   --- End of inner exception stack trace ---
   at RabbitMQ.Client.ConnectionFactory.CreateConnectionAsync(IEndpointResolver endpointResolver, String clientProvidedName, CancellationToken cancellationToken)

Reproduction steps

I am using 7.2.0.0 with the following logic to create the connection:

var factory = new ConnectionFactory
{
	ClientProvidedName = $"rabbitmq-client-{Environment.MachineName.ToLowerInvariant()}",
	UserName = settings.RabbitMqUser,
	Password = settings.RabbitMqPassword
};

if (!string.IsNullOrWhiteSpace(settings.RabbitMqCertFile))
{
	factory.Ssl.Enabled = true;
	factory.Ssl.ServerName = settings.RabbitMqCertServerName;
	factory.Ssl.Certs = [new X509Certificate2(
		settings.RabbitMqCertFile,
		settings.RabbitMqCertPass,
		X509KeyStorageFlags.MachineKeySet)];
	factory.Ssl.CertPath = settings.RabbitMqCertFile;
	factory.Ssl.CertPassphrase = settings.RabbitMqCertPass;

	factory.Ssl.AcceptablePolicyErrors =
		System.Net.Security.SslPolicyErrors.RemoteCertificateNameMismatch
		| System.Net.Security.SslPolicyErrors.RemoteCertificateChainErrors;
}

_connection = await factory.CreateConnectionAsync(settings.RabbitMqHosts);

Expected behavior

There should be no exception with the assumption that the target/3rd party server is up and running (and there is no firewall issue)

Additional context

No response

[michaelklishin]

There is nothing for the maintainers to work on in this "bug report".
We won't guess what specifically tripped up the connection.

We have no server log entries when connection fails, no server version information, no details on whether the default guest user is known (it has intentional connectivity limitations).