MQTTnet/Source/MQTTnet.Server/appsettings.json

{
  "MQTTnetServer": {
    /*
     Wildcard Addresses:
      *           - All local IP addresses
      localhost   - Localhost only

     Supported Protocols:
      0           - HTTP
      1           - HTTPS
      20          - MQTT
    */
    "Listen": [
      {
        "Address": "localhost",
        "Port": 5000,
        "Protocol": 0
      },
      {
        "Address": "*",
        "Port": 1883,
        "Protocol": 20
      }
    ]
  },
  "Logging": {
    "LogLevel": {
      "Default": "Warning"
    }
  },
  "AllowedHosts": "*"
}