Unicode characters with lstlisting

Question

In UTF-8 it should be possible to use ä and ö.

But actually in my code listing I use the package listings I receive by this example

\lstset{language=HTML}
 % Set your language (you can change the language for each code-block optionally)
\begin{lstlisting}[caption=Socket Connection, frame=single]  % Start your code-block
// einbinden der Library mittels CommonJs
var net = require('net');
// Socket Client erstellen
var client = new net.Socket();
// mit dem Server verbinden IP Port angeben
client.connect(<PORT>, '<IP>', function() {
    console.log('Connected');
    client.write('Hello, server! Love, Client.');
});
// verschiedene Events Listener
// dieser wird ausgelöst s der Server Daten zum Client sendet 
client.on('data', function(data) {
    console.log('Received: ' + data);
    client.destroy(); // kill client after server's response
});
client.on('close', function() {
    console.log('Connection closed');
});
\end{lstlisting}

the error message

! Package inputenc Error: Invalid UTF-8 byte sequence.

And it is denoting to the line with the 'ö' // dieser wird ausgelöst s der Server Daten zum Client sendet

Note: Sure I know it isn't HTML but when I say JavaScript it doesn't work

In the preamble I say

\usepackage[utf8]{inputenc} % Unicode Text