Expose configuration of packet fragmentation in server options. (#1769)

Author: chkr1011

.github/workflows/ReleaseNotes.md

@@ -1,2 +1,3 @@
 * [Client] Fixed _PlatformNotSupportedException_ when using Blazor (#1755, thanks to @Nickztar).
 * [Server] Fixed _NullReferenceException_ in retained messages management (#1762, thanks to @logicaloud).
+* [Server] Exposed new option which allows disabling packet fragmentation (#1753).

Source/MQTTnet/Implementations/MqttTcpServerListener.cs

@@ -231,6 +231,7 @@ await sslStream.AuthenticateAsServerAsync(
 
  using (var clientAdapter = new MqttChannelAdapter(tcpChannel, packetFormatterAdapter, _rootLogger))
  {
+ clientAdapter.AllowPacketFragmentation = _options.AllowPacketFragmentation;
  await clientHandler(clientAdapter).ConfigureAwait(false);
  }
  }
@@ -255,6 +256,7 @@ await sslStream.AuthenticateAsServerAsync(
  {
  try
  {
+ // ReSharper disable once MethodHasAsyncOverload
  stream?.Dispose();
  clientSocket?.Dispose();
  }

Source/MQTTnet/Server/Options/MqttServerOptionsBuilder.cs

@@ -131,6 +131,18 @@ public MqttServerOptionsBuilder WithoutEncryptedEndpoint()
  return this;
  }
 
+ /// <summary>
+ /// Usually the MQTT packets can be send partially to improve memory allocations.
+ /// This is done by using multiple TCP packets or WebSocket frames etc.
+ /// Unfortunately not all clients do support this and will close the connection when receiving partial packets.
+ /// </summary>
+ public MqttServerOptionsBuilder WithoutPacketFragmentation()
+ {
+ _options.DefaultEndpointOptions.AllowPacketFragmentation = false;
+ _options.TlsEndpointOptions.AllowPacketFragmentation = false;
+ return this;
+ }
+
  public MqttServerOptionsBuilder WithPersistentSessions(bool value = true)
  {
  _options.EnablePersistentSessions = value;

Source/MQTTnet/Server/Options/MqttServerTcpEndpointBaseOptions.cs

@@ -23,6 +23,14 @@ public abstract class MqttServerTcpEndpointBaseOptions
  /// </summary>
  public bool? KeepAlive { get; set; }
 
+ /// <summary>
+ /// Usually the MQTT packets can be send partially. This is done by using multiple TCP packets
+ /// or WebSocket frames etc. Unfortunately not all clients do support this feature and
+ /// will close the connection when receiving such packets. If such clients are connecting to this
+ /// server the flag must be set to _false_.
+ /// </summary>
+ public bool AllowPacketFragmentation { get; set; } = true;
+
  /// <summary>
  /// Gets or sets the TCP keep alive interval.
  /// The value _null_ indicates that the OS and framework defaults should be used.