Add benchmark app.

Tests/MQTTnet.Benchmarks/MessageProcessingBenchmark.cs

@@ -0,0 +1,47 @@
+using BenchmarkDotNet.Attributes;
+using BenchmarkDotNet.Attributes.Columns;
+using BenchmarkDotNet.Attributes.Exporters;
+using BenchmarkDotNet.Attributes.Jobs;
+using MQTTnet.Client;
+using MQTTnet.Server;
+
+namespace MQTTnet.Benchmarks
+{
+    [ClrJob]
+    [RPlotExporter, RankColumn]
+    public class MessageProcessingBenchmark
+    {
+        private IMqttServer _mqttServer;
+        private IMqttClient _mqttClient;
+        private MqttApplicationMessage _message;
+
+        [GlobalSetup]
+        public void Setup()
+        {
+            var factory = new MqttFactory();
+            _mqttServer = factory.CreateMqttServer();
+            _mqttClient = factory.CreateMqttClient();
+
+            var serverOptions = new MqttServerOptionsBuilder().Build();
+            _mqttServer.StartAsync(serverOptions).GetAwaiter().GetResult();
+
+            var clientOptions = new MqttClientOptionsBuilder()
+                .WithTcpServer("localhost").Build();
+
+            _mqttClient.ConnectAsync(clientOptions).GetAwaiter().GetResult();
+
+            _message = new MqttApplicationMessageBuilder()
+                .WithTopic("A")
+                .Build();
+        }
+
+        [Benchmark]
+        public void Send_10000_Messages()
+        {
+            for (var i = 0; i < 10000; i++)
+            {
+                _mqttClient.PublishAsync(_message).GetAwaiter().GetResult();
+            }
+        }
+    }
+}