TCP connection refused when hosted in IIS - asp.net-core

Question

I have a ASP.NET Core website that listens on 8801 port for normal HTTP request. This program also listens on the 8803 port for MQTT TCP connection.
If I run the progam with Kestrel directly on the server as below:
dotnet MyWebsite.dll # runs the command on the server
I can connect the remote 8803 port with my client successfully. So if I understand it correctly :
The MQTT Server does work fine when using Kestrel.
The 8803 port is not banned by the firewall.
The MQTT TCP Server can accept connection from my client.
However, when hosting within IIS (in-process or out-of-process), the TCP server doesn't work any more:
logs when using MQTT.fx:
2020-08-06 14:14:03,864 INFO --- BrokerConnectorController :
onConnect 2020-08-06 14:14:03,865 INFO --- ScriptsController
: Clear console. 2020-08-06 14:14:03,868 INFO --- MqttFX ClientModel
: MqttClient with ID MQTT_FX_Client assigned. 2020-08-06 14:14:08,100
ERROR --- MqttFX ClientModel : Error when connecting
org.eclipse.paho.client.mqttv3.MqttException: Unable to connect to
server at
org.eclipse.paho.client.mqttv3.internal.TCPNetworkModule.start(TCPNetworkModule.java:94)
~[org.eclipse.paho.client.mqttv3-1.2.0.jar:?] at
org.eclipse.paho.client.mqttv3.internal.ClientComms$ConnectBG.run(ClientComms.java:701)
~[org.eclipse.paho.client.mqttv3-1.2.0.jar:?] at
java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
~[?:1.8.0_181] at java.util.concurrent.FutureTask.run(Unknown Source)
~[?:1.8.0_181] at
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(Unknown
Source) ~[?:1.8.0_181] at
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown
Source) ~[?:1.8.0_181] at
java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
[?:1.8.0_181] at
java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
[?:1.8.0_181] at java.lang.Thread.run(Unknown Source) [?:1.8.0_181]
Caused by: java.net.ConnectException: Connection refused: connect at
java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
~[?:1.8.0_181] at
java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
~[?:1.8.0_181] at java.net.AbstractPlainSocketImpl.doConnect(Unknown
Source) ~[?:1.8.0_181] at
java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
~[?:1.8.0_181] at java.net.AbstractPlainSocketImpl.connect(Unknown
Source) ~[?:1.8.0_181] at java.net.PlainSocketImpl.connect(Unknown
Source) ~[?:1.8.0_181] at java.net.SocksSocketImpl.connect(Unknown
Source) ~[?:1.8.0_181] at java.net.Socket.connect(Unknown Source)
~[?:1.8.0_181] at
org.eclipse.paho.client.mqttv3.internal.TCPNetworkModule.start(TCPNetworkModule.java:84)
~[org.eclipse.paho.client.mqttv3-1.2.0.jar:?] ... 8 more 2020-08-06
14:14:08,102 ERROR --- MqttFX ClientModel : Please verify
your Settings (e.g. Broker Address, Broker Port & Client ID) and the
user credentials! org.eclipse.paho.client.mqttv3.MqttException: Unable
to connect to server at
org.eclipse.paho.client.mqttv3.internal.TCPNetworkModule.start(TCPNetworkModule.java:94)
~[org.eclipse.paho.client.mqttv3-1.2.0.jar:?] at
org.eclipse.paho.client.mqttv3.internal.ClientComms$ConnectBG.run(ClientComms.java:701)
~[org.eclipse.paho.client.mqttv3-1.2.0.jar:?] at
java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
~[?:1.8.0_181] at java.util.concurrent.FutureTask.run(Unknown Source)
~[?:1.8.0_181] at
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(Unknown
Source) ~[?:1.8.0_181] at
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown
Source) ~[?:1.8.0_181] at
java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
[?:1.8.0_181] at
java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
[?:1.8.0_181] at java.lang.Thread.run(Unknown Source) [?:1.8.0_181]
Caused by: java.net.ConnectException: Connection refused: connect at
java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
~[?:1.8.0_181] at
java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
~[?:1.8.0_181] at java.net.AbstractPlainSocketImpl.doConnect(Unknown
Source) ~[?:1.8.0_181] at
java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
~[?:1.8.0_181] at java.net.AbstractPlainSocketImpl.connect(Unknown
Source) ~[?:1.8.0_181] at java.net.PlainSocketImpl.connect(Unknown
Source) ~[?:1.8.0_181] at java.net.SocksSocketImpl.connect(Unknown
Source) ~[?:1.8.0_181] at java.net.Socket.connect(Unknown Source)
~[?:1.8.0_181] at
org.eclipse.paho.client.mqttv3.internal.TCPNetworkModule.start(TCPNetworkModule.java:84)
~[org.eclipse.paho.client.mqttv3-1.2.0.jar:?] ... 8 more 2020-08-06
14:14:08,111 INFO --- ScriptsController : Clear console.
2020-08-06 14:14:08,112 ERROR --- BrokerConnectService :
Actually, I cann't connect to server:8803 with normal tcp client.
I'm using MQTTnet(3.0.11) + ASP.NET Core(2.1):
public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
WebHost.CreateDefaultBuilder(args)
.UseKestrel(opts => {
opts.ListenAnyIP(8803, l => l.UseMqtt());
opts.ListenAnyIP(8801);
})
.ConfigureLogging((hostingContext, logging) =>
{
// ...
})
.UseStartup<Startup>();
The HTTP Website works fine (8801).
I can't connect to the MQTT Server (8803) when hosted within IIS.
So my question is : why it happens? How can I host the program with IIS ?
If you need more information, please let me know.

Answer 1

I suggest you could try to use another way to create the MSQT server, and make sure you have open the right port to allow access.
Startup.cs:
var mqttServerOptions = new MqttServerOptionsBuilder() .WithDefaultEndpointPort(1883) .Build(); services .AddHostedMqttServer(mqttServerOptions) .AddMqttConnectionHandler() .AddConnections() .AddMqttTcpServerAdapter();