How do I import dart:html & dart:io in the same class?

Question

The code below "looks right", it compiles, but does not run, failing with the console message:

Cannot load Dart script dart:io
Failed to load resource

If I comment out the #import('dart:io');, wrong I believe, I get a compilation error, but it launches and not until I press the button, do I get the runtime error:

Internal error: 'http://127.0.0.1:3030/home/david/dart/samples/htmlIO/htmlIO.dart': Error: line 13 pos 26: type 'HttpClient' is not loaded
var connection = new HttpClient().get('www.google.com', 80, '/');

... which is expected.

So my question is: How do I import dart:html & dart:io in the same class?

#import('dart:html');
#import('dart:io');

class htmlIO {

  ButtonElement _aButton;

  htmlIO() {
  }

  void handlePress(Event e) {
    var connection = new HttpClient().get('www.google.com', 80, '/');
    write('made it');
  }

  void run() {
    _aButton = document.query("#aButton");
    _aButton.on.click.add(handlePress);
    write("Hello World!");
  }

  void write(String message) {
    // the HTML library defines a global "document" variable
    document.query('#status').innerHTML = message;
  }
}

void main() {
  new htmlIO().run();
}

Answer 1

dart:html is a client side library, whereas dart:io is a server side library. dart:html makes use of features of the browser, but dart:io makes use of features that are restricted by browser security (such as file system access an so-on).

It may be that the time comes that you can use dart:html on the server, with a "mocked" browser, which could be useful for unit testing and the like, but you can't do that yet.