diff --git a/Build/MQTTnet.nuspec b/Build/MQTTnet.nuspec
index 67feb06..eaf178c 100644
--- a/Build/MQTTnet.nuspec
+++ b/Build/MQTTnet.nuspec
@@ -11,6 +11,7 @@
     <requireLicenseAcceptance>false</requireLicenseAcceptance>
     <description>MQTTnet is a high performance .NET library for MQTT based communication. It provides a MQTT client and a MQTT server (broker) and supports v3.1.0, v3.1.1 and v5.0.0 of the MQTT protocol.</description>
     <releaseNotes>
+* [ManagedClient] Added support for persisted sessions (thansk to @PMExtra).
 * [Client] Improve connection stability (thanks to @jltjohanlindqvist).
 * [ManagedClient] Fixed a memory leak (thanks to @zawodskoj).
 * [ManagedClient] Improved internal subscription management (#569, thanks to @cstichlberger).
diff --git a/Build/build.ps1 b/Build/build.ps1
index bd193d6..36c6eab 100644
--- a/Build/build.ps1
+++ b/Build/build.ps1
@@ -13,11 +13,11 @@ Write-Host "MSBuild path     = $msbuild"
 Write-Host
 
 # Build and execute tests
-&$msbuild ..\Tests\MQTTnet.Core.Tests\MQTTnet.Tests.csproj /t:Build /p:Configuration="Release" /p:TargetFramework="netcoreapp2.1" /verbosity:m
-&$msbuild ..\Tests\MQTTnet.AspNetCore.Tests\MQTTnet.AspNetCore.Tests.csproj /t:Build /p:Configuration="Release" /p:TargetFramework="netcoreapp2.1" /verbosity:m
+&$msbuild ..\Tests\MQTTnet.Core.Tests\MQTTnet.Tests.csproj /t:Build /p:Configuration="Release" /p:TargetFramework="netcoreapp3.1" /verbosity:m
+&$msbuild ..\Tests\MQTTnet.AspNetCore.Tests\MQTTnet.AspNetCore.Tests.csproj /t:Build /p:Configuration="Release" /p:TargetFramework="netcoreapp3.1" /verbosity:m
 
-vstest.console.exe ..\Tests\MQTTnet.Core.Tests\bin\Release\netcoreapp2.1\MQTTnet.Tests.dll
-vstest.console.exe ..\Tests\MQTTnet.AspNetCore.Tests\bin\Release\netcoreapp2.1\MQTTnet.AspNetCore.Tests.dll
+vstest.console.exe ..\Tests\MQTTnet.Core.Tests\bin\Release\netcoreapp3.1\MQTTnet.Tests.dll
+vstest.console.exe ..\Tests\MQTTnet.AspNetCore.Tests\bin\Release\netcoreapp3.1\MQTTnet.AspNetCore.Tests.dll
 
 # Build the core library
 &$msbuild ..\Source\MQTTnet\MQTTnet.csproj /t:Build /p:Configuration="Release" /p:TargetFramework="net452" /p:FileVersion=$assemblyVersion /p:AssemblyVersion=$assemblyVersion /verbosity:m /p:SignAssembly=true /p:AssemblyOriginatorKeyFile=".\..\..\Build\codeSigningKey.pfx"
@@ -84,7 +84,7 @@ Remove-Item "nuget.exe" -Force -Recurse -ErrorAction SilentlyContinue
 # Build MQTTnet.Server Portable
 &dotnet publish ..\Source\MQTTnet.Server\MQTTnet.Server.csproj --configuration Release /p:FileVersion=$assemblyVersion /p:Version=$nugetVersion
 
-$source = "..\Source\MQTTnet.Server\bin\Release\netcoreapp2.2\publish"
+$source = "..\Source\MQTTnet.Server\bin\Release\netcoreapp3.1\publish"
 $destination = "..\Source\MQTTnet.Server\bin\MQTTnet.Server-Portable-v$nugetVersion.zip"
 If(Test-path $destination) {Remove-item $destination}
  Add-Type -assembly "system.io.compression.filesystem"
@@ -95,7 +95,7 @@ If(Test-path $destination) {Remove-item $destination}
 # Build MQTTnet.Server Linux-x64
 &dotnet publish ..\Source\MQTTnet.Server\MQTTnet.Server.csproj --configuration Release /p:FileVersion=$assemblyVersion /p:Version=$nugetVersion --self-contained --runtime linux-x64 
 
-$source = "..\Source\MQTTnet.Server\bin\Release\netcoreapp2.2\linux-x64\publish"
+$source = "..\Source\MQTTnet.Server\bin\Release\netcoreapp3.1\linux-x64\publish"
 $destination = "..\Source\MQTTnet.Server\bin\MQTTnet.Server-Linux-x64-v$nugetVersion.zip"
 If(Test-path $destination) {Remove-item $destination}
  Add-Type -assembly "system.io.compression.filesystem"
@@ -106,7 +106,7 @@ If(Test-path $destination) {Remove-item $destination}
 # Build MQTTnet.Server Linux-ARM
 &dotnet publish ..\Source\MQTTnet.Server\MQTTnet.Server.csproj --configuration Release /p:FileVersion=$assemblyVersion /p:Version=$nugetVersion --self-contained --runtime linux-arm 
 
-$source = "..\Source\MQTTnet.Server\bin\Release\netcoreapp2.2\linux-ARM\publish"
+$source = "..\Source\MQTTnet.Server\bin\Release\netcoreapp3.1\linux-ARM\publish"
 $destination = "..\Source\MQTTnet.Server\bin\MQTTnet.Server-Linux-ARM-v$nugetVersion.zip"
 If(Test-path $destination) {Remove-item $destination}
  Add-Type -assembly "system.io.compression.filesystem"
@@ -117,7 +117,7 @@ If(Test-path $destination) {Remove-item $destination}
 # Build MQTTnet.Server Windows-x64
 &dotnet publish ..\Source\MQTTnet.Server\MQTTnet.Server.csproj --configuration Release /p:FileVersion=$assemblyVersion /p:Version=$nugetVersion --self-contained --runtime win-x64
 
-$source = "..\Source\MQTTnet.Server\bin\Release\netcoreapp2.2\win-x64\publish"
+$source = "..\Source\MQTTnet.Server\bin\Release\netcoreapp3.1\win-x64\publish"
 $destination = "..\Source\MQTTnet.Server\bin\MQTTnet.Server-Windows-x64-v$nugetVersion.zip"
 If(Test-path $destination) {Remove-item $destination}
  Add-Type -assembly "system.io.compression.filesystem"
diff --git a/Source/MQTTnet.Server/MQTTnet.Server.csproj b/Source/MQTTnet.Server/MQTTnet.Server.csproj
index bbd3ceb..4235315 100644
--- a/Source/MQTTnet.Server/MQTTnet.Server.csproj
+++ b/Source/MQTTnet.Server/MQTTnet.Server.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp2.2</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
     <AspNetCoreHostingModel>InProcess</AspNetCoreHostingModel>
     <AssemblyName>MQTTnet.Server</AssemblyName>
     <RootNamespace>MQTTnet.Server</RootNamespace>
diff --git a/Source/MQTTnet.Server/Web/Startup.cs b/Source/MQTTnet.Server/Web/Startup.cs
index 8ef622e..2beb771 100644
--- a/Source/MQTTnet.Server/Web/Startup.cs
+++ b/Source/MQTTnet.Server/Web/Startup.cs
@@ -1,8 +1,4 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Net;
-using Microsoft.AspNetCore.Authentication;
+using Microsoft.AspNetCore.Authentication;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Mvc;
@@ -16,7 +12,12 @@ using MQTTnet.Server.Logging;
 using MQTTnet.Server.Mqtt;
 using MQTTnet.Server.Scripting;
 using MQTTnet.Server.Scripting.DataSharing;
+using Newtonsoft.Json.Converters;
 using Swashbuckle.AspNetCore.SwaggerUI;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net;
 
 namespace MQTTnet.Server.Web
 {
@@ -88,10 +89,10 @@ namespace MQTTnet.Server.Web
             services.AddCors();
 
             services.AddMvc()
-                .SetCompatibilityVersion(CompatibilityVersion.Version_2_2)
-                .AddJsonOptions(options =>
+                .SetCompatibilityVersion(CompatibilityVersion.Version_3_0)
+                .AddNewtonsoftJson(o =>
                 {
-                    options.SerializerSettings.Converters.Add(new Newtonsoft.Json.Converters.StringEnumConverter());
+                    o.SerializerSettings.Converters.Add(new StringEnumConverter());
                 });
 
             ReadMqttSettings(services);
@@ -116,7 +117,7 @@ namespace MQTTnet.Server.Web
             services.AddSwaggerGen(c =>
             {
                 c.DescribeAllEnumsAsStrings();
-                
+
                 var securityScheme = new OpenApiSecurityScheme
                 {
                     Scheme = "Basic",
diff --git a/Tests/MQTTnet.AspNetCore.Tests/MQTTnet.AspNetCore.Tests.csproj b/Tests/MQTTnet.AspNetCore.Tests/MQTTnet.AspNetCore.Tests.csproj
index 13bb3d5..06b5976 100644
--- a/Tests/MQTTnet.AspNetCore.Tests/MQTTnet.AspNetCore.Tests.csproj
+++ b/Tests/MQTTnet.AspNetCore.Tests/MQTTnet.AspNetCore.Tests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp2.2</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
     <IsPackable>false</IsPackable>
   </PropertyGroup>
 
diff --git a/Tests/MQTTnet.Core.Tests/MQTTnet.Tests.csproj b/Tests/MQTTnet.Core.Tests/MQTTnet.Tests.csproj
index 7bf14cb..c0749f7 100644
--- a/Tests/MQTTnet.Core.Tests/MQTTnet.Tests.csproj
+++ b/Tests/MQTTnet.Core.Tests/MQTTnet.Tests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.2;net461</TargetFrameworks>
+    <TargetFramework>netcoreapp3.1;net461</TargetFramework>
     <IsPackable>false</IsPackable>
   </PropertyGroup>
 
diff --git a/Tests/MQTTnet.TestApp.AspNetCore2/MQTTnet.TestApp.AspNetCore2.csproj b/Tests/MQTTnet.TestApp.AspNetCore2/MQTTnet.TestApp.AspNetCore2.csproj
index 391a044..5c0aacd 100644
--- a/Tests/MQTTnet.TestApp.AspNetCore2/MQTTnet.TestApp.AspNetCore2.csproj
+++ b/Tests/MQTTnet.TestApp.AspNetCore2/MQTTnet.TestApp.AspNetCore2.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp2.1</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
     <TypeScriptToolsVersion>Latest</TypeScriptToolsVersion>
   </PropertyGroup>
 
diff --git a/Tests/MQTTnet.TestApp.UniversalWindows/MQTTnet.TestApp.UniversalWindows.csproj b/Tests/MQTTnet.TestApp.UniversalWindows/MQTTnet.TestApp.UniversalWindows.csproj
index 243c9c5..f31fe3b 100644
--- a/Tests/MQTTnet.TestApp.UniversalWindows/MQTTnet.TestApp.UniversalWindows.csproj
+++ b/Tests/MQTTnet.TestApp.UniversalWindows/MQTTnet.TestApp.UniversalWindows.csproj
@@ -11,7 +11,7 @@
     <AssemblyName>MQTTnet.TestApp.UniversalWindows</AssemblyName>
     <DefaultLanguage>en-US</DefaultLanguage>
     <TargetPlatformIdentifier>UAP</TargetPlatformIdentifier>
-    <TargetPlatformVersion Condition=" '$(TargetPlatformVersion)' == '' ">10.0.17134.0</TargetPlatformVersion>
+    <TargetPlatformVersion Condition=" '$(TargetPlatformVersion)' == '' ">10.0.18362.0</TargetPlatformVersion>
     <TargetPlatformMinVersion>10.0.10240.0</TargetPlatformMinVersion>
     <MinimumVisualStudioVersion>14</MinimumVisualStudioVersion>
     <FileAlignment>512</FileAlignment>