ConnectAsync fails when many Tasks are active

Describe the bug

For load tests we created an application that contains of a lot of Tasks (via Task.Run) which publish MQTT messages. Unfortunately ConnectAsync does not succeed to have a stable connection when a lot of Tasks are active. Note that the CPU load was very low since the Tasks didn’t do very much.

This may seem like a “toy code” problem. But our production application has the same problems, too. As soon as a few dozen Tasks are running an MQTT connection is not possible anymore.

Which project is your bug related to?

• Client (3.0.11.0 .NET 4.5.2)

To Reproduce

Steps to reproduce the behavior:

1. Create 100 Tasks
2. Connect to an MQTT broker
3. Connect won’t succeed

Expected behavior

ConnectAsync would be successful

### Code example
 Please provide full code examples below where possible to make it easier for the developers to check your issues.
 
```csharp
            // LOGGING
            MqttNetGlobalLogger.LogMessagePublished += (s, e) =>
            {
                var trace = $">> [{e.TraceMessage.Timestamp:O}] [{e.TraceMessage.ThreadId}] [{e.TraceMessage.Source}] [{e.TraceMessage.Level}]: {e.TraceMessage.Message}";
                if (e.TraceMessage.Exception != null)
                {
                    trace += Environment.NewLine + e.TraceMessage.Exception.ToString();
                }

                Console.WriteLine(trace);
            };

            // CREATE TASKS (which do almost nothing)
            bool run = true;

            for (int i = 0; i < 100; i++)
            {
                Task.Run(() =>
                {
                    while (run)
                    {
                        Thread.Sleep(100);
                    }
                });
            }

            Thread.Sleep(10000);

            // CONNECTING
            var options = new MqttClientOptionsBuilder()
                .WithClientId(Guid.NewGuid().ToString())
                .WithTcpServer("localhost",1883)
                .WithCleanSession()
                .Build();

            var result = mqttClient.ConnectAsync(options).Result;  // THIS WILL NOT SUCCEED

            Thread.Sleep(10000);
            run = false;

[OidaTiftla]

I’m glad I could help.

[SeppPenner]

Good to know that this is solved. Thank you @OidaTiftla. By the way, cool user name 😅