HiveMQ socket error when publishing

Hi,
I am running HA 0.90.2 non-ssl, I recently installed the ‘Bundled MQTT Server & Web client’.
I can connect but get socket errors when trying to do a test publish from the web UI. I click connect on the web interface and get a green connection indicator but when I do a test publish it disconnects?

I have this in configuration.yaml

```
  - platform: mqtt
    state_topic: "homeassistant/indoor/temp"
    name: 'Indoor Temp'
    unit_of_measurement: "C"
```

I have this is ’ MQTT Server & Web client’ Config:

```
{
  "log_level": "info",
  "certfile": "fullchain.pem",
  "keyfile": "privkey.pem",
  "web": {
    "enabled": true,
    "ssl": false
  },
  "broker": {
    "enabled": true,
    "enable_ws": true,
    "enable_mqtt": true,
    "enable_ws_ssl": false,
    "enable_mqtt_ssl": false,
    "allow_anonymous": true
  },
  "mqttusers": [
    {
      "username": "fred",
      "password": "fred",
      "readonly": false,
      "topics": [
        "#homeassistant/indoor/temp"
      ]
    }
  ]
}
```

Log:

1554072209: New client connected from 192.168.1.8 as home-assistant (c1, k60, u’fred’).
1554072213: Socket error on client home-assistant, disconnecting.

UI Screenshot:

Any ideas why I get socket errors on publishing?