title: HttpException: Connection closed before full header was received
body: <p>I am trying to make post call as the code bellow shows. </p>
  
  <pre><code>  Map&lt;String, String&gt; header = {"Content-Type": "application/json"};
    Map&lt;String, String&gt; body = {
      "client_id": "xxxx",
      "client_secret": "XXXX",
      "password": "password",
      "username": "username",
    };
  
    Future&lt;Post&gt; callForFirstToken() async {
      final response = await http.post(url, headers: header, body: body);
      return response.statusCode == 200
        ? Post.fromJson(json.decode(response.body))
        : throw Exception('Failed to load ...');}
  </code></pre>
  
  <p>But, I have got this error:</p>
  
  <pre><code>Error connecting to the service protocol: HttpException: Connection closed before full header was received, uri = http://127.0.0.1:60556/sK_cPlYMcGQ=/ws
  </code></pre>