Site-www: Use browser access to trigger two requests

[cuichuanteng]

dart --version
Dart VM version: 2.6.1 (Mon Nov 11 13:12:24 2019 +0100) on "macos_x64"

import 'dart:io';

Future main() async {
  var server = await HttpServer.bind(
    InternetAddress('0.0.0.0'),
    4000,
  );
  print('Listening on localhost:${server.port}');

  await for (HttpRequest request in server) {
  // if you use browser will print twice
 //  if you use curl will print once
    print('request ${request.method}'); // why run twice???
    request.response
      ..write('Hello, world!')
      ..close();
  }
}

[kwalrath]

Could you please clarify what the problem is and what page is affected? Thanks!

[cuichuanteng]

This is a sample code and all the code. After running, visit http://127.0.0.1:4000 through the chrome browser, the console will see 2 printouts, but if you use curl http://127.0.0.1: 4000 will only output once.

[cuichuanteng]

@kwalrath

[kwalrath]

Looks like the affected files are https://dart.dev/tutorials/server/httpserver (src/_tutorials/server/httpserver.md) and possibly the following Dart files:

examples/httpserver/test/httpserver_test.dart
examples/httpserver/bin/hello_world_server_secure.dart
examples/httpserver/bin/hello_world_server.dart

[cuichuanteng]

看起来受影响的文件是https://dart.dev/tutorials/server/httpserver（src / _tutorials / server / httpserver.md）以及以下Dart文件：

示例/ httpserver /测试/httpserver_test.dart
示例/httpserver/bin/hello_world_server_secure.dart
示例/httpserver/bin/hello_world_server.dart

Can you reproduce this problem? Is this a bug? Or did I write it wrong?

[kwalrath]

Could you create a gist with your code and exact instructions on how you ran it and used the browser and curl? That way we can duplicate your work.

[cuichuanteng]

@kwalrath demo repository:https://github.com/cuichuanteng/dart-httpserver-demo.git

[cuichuanteng]

demo video

[kwalrath]

Thanks the video helps!

[theacodes]

Hi @cuichuanteng! The reason you're seeing two requests with the browser is because the browser actualy performs two separate requests - one for the page itself (/) and one for the page's favicon (/favicon.ico). You can verify this by modifying the code above to also print out the request's path:

import 'dart:io';

Future main() async {
  var server = await HttpServer.bind(
    InternetAddress('0.0.0.0'),
    4000,
  );
  print('Listening on localhost:${server.port}');

  await for (HttpRequest request in server) {
    print('request ${request.method}, ${request.uri.path}');
    request.response
      ..write('Hello, world!')
      ..close();
  }
}

Outputs this when using the browser:

Listening on localhost:4000
request GET, /
request GET, /favicon.ico

If you want to know more about favicons, check out this excellent wikipedia article. If you want to disable the favicon request, see this stackoverflow question.

[kwalrath]

Thank you, @theacodes!

[cuichuanteng]

Everyone thanks! @kwalrath @theacodes