diff --git a/app/src/components/ConnectionSetup/Connection.tsx b/app/src/components/ConnectionSetup/Connection.tsx
index cbbdc6b..1ef4723 100644
--- a/app/src/components/ConnectionSetup/Connection.tsx
+++ b/app/src/components/ConnectionSetup/Connection.tsx
@@ -1,9 +1,14 @@
 import * as React from 'react'
-import { Typography, Toolbar, Modal, MenuItem, Button, Grid, Paper, TextField, Switch, FormControlLabel } from '@material-ui/core'
+import {
+  Typography, Toolbar, Modal,
+  MenuItem, Button, Grid, Paper,
+  TextField, Switch, FormControlLabel,
+  CircularProgress,
+} from '@material-ui/core'
 import { withStyles, Theme, StyleRulesCallback } from '@material-ui/core/styles'
 import Notification from './Notification'
 import { MqttOptions, DataSourceState } from '../../../../backend/src/DataSource'
-import { addMqttConnectionEvent, makeConnectionStateEvent, rendererEvents } from '../../../../events'
+import { addMqttConnectionEvent, makeConnectionStateEvent, removeConnection, rendererEvents } from '../../../../events'
 import sha1 = require('sha1')
 
 interface Props {
@@ -14,18 +19,20 @@ interface Props {
 }
 
 const protocols = [
-  'tcp://',
+  'mqtt://',
   'ws://',
 ]
 
 interface State {
+  connecting: boolean
+  connectionId?: string
   error?: Error
   visible: boolean
   host: string
   protocol: string
   port: number
-  ssl: boolean
-  sslValidation: boolean
+  tls: boolean
+  certValidation: boolean
   clientId: string
   username: string
   password: string
@@ -49,11 +56,13 @@ class Connection extends React.Component<Props, State> {
       host: 'nodered',
       protocol: protocols[0],
       port: 1883,
-      ssl: false,
-      sslValidation: true,
+      tls: false,
+      certValidation: true,
       clientId: '',
       username: '',
       password: '',
+      connecting: false,
+      connectionId: undefined,
     }
 
     this.state = Object.assign({}, defaultState, storedSettings)
@@ -71,16 +80,24 @@ class Connection extends React.Component<Props, State> {
       url,
       username: this.state.username || undefined,
       password: this.state.username || undefined,
-      ssl: this.state.ssl,
-      sslValidation: this.state.sslValidation,
+      tls: this.state.tls,
+      certValidation: this.state.certValidation,
     }
   }
 
   private connect() {
+    this.setState({
+      connecting: true,
+    })
+
     const options = this.optionsFromState()
     const connectionId = (sha1(Math.random() + JSON.stringify(options)).slice(0, 8)) as string
+    this.setState({ connectionId })
     rendererEvents.emit(addMqttConnectionEvent, { options, id: connectionId })
-    rendererEvents.subscribe(makeConnectionStateEvent(connectionId), (state: DataSourceState) => {
+    const event = makeConnectionStateEvent(connectionId)
+
+    rendererEvents.subscribe(event, (state: DataSourceState) => {
+      console.log(state)
       if (state.connected) {
         this.props.onConnection(connectionId)
         this.setState({ visible: false })
@@ -91,6 +108,13 @@ class Connection extends React.Component<Props, State> {
     })
   }
 
+  private disconnect() {
+    this.setState({
+      connecting: false,
+    })
+    rendererEvents.emit(removeConnection, this.state.connectionId)
+  }
+
   public static styles: StyleRulesCallback<string> = (theme: Theme) => {
     return {
       root: {
@@ -130,6 +154,7 @@ class Connection extends React.Component<Props, State> {
 
   public render() {
     const { classes } = this.props
+
     return <Modal open={this.state.visible} disableAutoFocus={true} onClose={() => { console.log('close') }}>
         <Paper className={classes.root}>
           <Toolbar>
@@ -190,13 +215,13 @@ class Connection extends React.Component<Props, State> {
                   margin="normal"
                 />
               </Grid>
-              <Grid item xs={3}>
+              <Grid item xs={4}>
                 <div className={classes.switch}>
                   <FormControlLabel
                     control={(
                       <Switch
-                        checked={this.state.sslValidation}
-                        onChange={() => this.setState({ sslValidation: !this.state.sslValidation })}
+                        checked={this.state.certValidation}
+                        onChange={() => this.setState({ certValidation: !this.state.certValidation })}
                         color="primary"
                       />
                     )}
@@ -205,36 +230,55 @@ class Connection extends React.Component<Props, State> {
                   />
                 </div>
               </Grid>
-              <Grid item xs={3}>
+              <Grid item xs={4}>
                 <div className={classes.switch}>
                   <FormControlLabel
                     control={(
                       <Switch
-                        checked={this.state.ssl}
-                        onChange={() => this.setState({ ssl: !this.state.ssl })}
+                        checked={this.state.tls}
+                        onChange={() => this.setState({ tls: !this.state.tls })}
                         color="primary"
                       />
                     )}
-                    label="Encryption"
+                    label="Encryption (tls)"
                     labelPlacement="bottom"
                   />
                 </div>
               </Grid>
-              <Grid item xs={6}></Grid>
+              <Grid item xs={4}></Grid>
             </Grid>
             <br />
             <div style={{ textAlign: 'right' }}>
               <Button variant="contained" color="secondary" className={classes.button} onClick={() => this.saveConnectionSettings()}>
                 Save
               </Button>
-              <Button variant="contained" color="primary" className={classes.button} onClick={() => this.connect()}>
-                Connect
-              </Button>
+              { this.renderConnectButton() }
             </div>
           </form>
         </Paper>
     </Modal>
   }
+
+  private renderConnectButton() {
+    const { classes } = this.props
+
+    if (this.state.connecting) {
+      return <Button variant="contained" color="primary" className={classes.button} onClick={this.onClickAbort}>
+        <CircularProgress size={22} style={{ marginRight: '10px' }} color="secondary" /> Abort
+      </Button>
+    }
+    return <Button variant="contained" color="primary" className={classes.button} onClick={this.onClickConnect}>
+      Connect
+    </Button>
+  }
+
+  private onClickConnect = () => {
+    this.connect()
+  }
+
+  private onClickAbort = () => {
+    this.disconnect()
+  }
 }
 
 export default withStyles(Connection.styles, { withTheme: true })(Connection)
diff --git a/backend/src/DataSource/MqttSource.ts b/backend/src/DataSource/MqttSource.ts
index 9b4360d..0d6cf5c 100644
--- a/backend/src/DataSource/MqttSource.ts
+++ b/backend/src/DataSource/MqttSource.ts
@@ -1,12 +1,13 @@
 import { Client, connect as mqttConnect } from 'mqtt'
 import { DataSource, DataSourceStateMachine } from './'
+import * as Url from 'url'
 
 export interface MqttOptions {
   url: string
   username?: string
   password?: string
-  ssl: boolean
-  sslValidation: boolean
+  tls: boolean
+  certValidation: boolean
 }
 
 export class MqttSource implements DataSource<MqttOptions> {
@@ -22,13 +23,25 @@ export class MqttSource implements DataSource<MqttOptions> {
 
   public connect(options: MqttOptions): DataSourceStateMachine {
     this.stateMachine.setConnecting()
-    const client = mqttConnect(options.url, {
+
+    const urlStr = options.tls ? options.url.replace(/^(mqtt|ws):/, '$1s:') : options.url
+    let url
+    try {
+      url = Url.parse(urlStr)
+    } catch (error) {
+      this.stateMachine.setError(error)
+      throw error
+    }
+
+    const client = mqttConnect(url, {
       resubscribe: false,
+      rejectUnauthorized: !options.certValidation,
     })
 
     this.client = client
 
     client.on('error', (error: Error) => {
+      console.log(error)
       this.stateMachine.setError(error)
     })
 
diff --git a/backend/src/index.ts b/backend/src/index.ts
index 1f6509b..dc7a97a 100644
--- a/backend/src/index.ts
+++ b/backend/src/index.ts
@@ -1,4 +1,8 @@
-import { addMqttConnectionEvent, backendEvents, makeConnectionStateEvent, makeConnectionMessageEvent, AddMqttConnection } from '../../events'
+import {
+  addMqttConnectionEvent, backendEvents,
+  makeConnectionStateEvent, removeConnection,
+  makeConnectionMessageEvent, AddMqttConnection
+} from '../../events'
 import { MqttSource, DataSource } from './DataSource'
 
 class ConnectionManager {
@@ -6,17 +10,18 @@ class ConnectionManager {
 
   public manageConnections() {
     backendEvents.subscribe(addMqttConnectionEvent, this.handleConnectionRequest)
+    backendEvents.subscribe(removeConnection, (connectionId) => this.removeConnection(connectionId))
   }
 
   private handleConnectionRequest = (event: AddMqttConnection) => {
-    console.log(event)
     const connectionId = event.id
     const options = event.options
     const connection = new MqttSource()
     this.connections[connectionId] = connection
 
+    const connectionStateEvent = makeConnectionStateEvent(connectionId)
     connection.stateMachine.onUpdate.subscribe((state) => {
-      backendEvents.emit(makeConnectionStateEvent(connectionId), state)
+      backendEvents.emit(connectionStateEvent, state)
     })
 
     connection.connect(options)
@@ -36,7 +41,6 @@ class ConnectionManager {
 
   public removeConnection(hash: string) {
     const connection = this.connections[hash]
-    connection.stateMachine
     connection.disconnect()
     delete this.connections[hash]
   }