如何从 dart:io 服务器上的 HTTPRequest 读取文件

Question

I am trying to create a server to run locally for my application to upload some files while debugging. It is very simple and the full source code is:

import 'dart:io';

void main(List<String> arguments) async {
  const port = 8080;
  final server = await HttpServer.bind(InternetAddress.anyIPv4, port);
  server.listen((request) async {
    if (request.uri.path != '/save_screenshot' || request.method != 'POST') {
      request.response.statusCode = 404;
      request.response.close();
      return;
    }

    // TODO: read the file
    request.response.statusCode = 200;
    request.response.close();
  });
  print('screenshot server listening on $port.');
}

At the code there is a TODO comment, where I would like to read the file from the HTTPRequest, I googled a bit and could not find a example to copy. Does anyone know how to read the file from the HTTPRequest?

Here is how it is being sent (on the client side):

final url = 'http://<local_ip_address>:8080/save_screenshot';
var request = http.MultipartRequest('POST', Uri.parse(url));
request.files.add(
  http.MultipartFile.fromBytes(
    'file',
    screenshot.bytes,
    filename: 'screenshot.png',
  ),
);
await request.send();

Answer 1

I found out how to read the file from the HTTPRequest. But for it to work it is necessary to install a package called mime .

Then replace the TODO comment in the question with:

final boundary = request.headers.contentType!.parameters['boundary']!;
final mimeTransformer = MimeMultipartTransformer(boundary);
final parts = request.cast<List<int>>().transform(mimeTransformer);
await for (final part in parts) {
  final file = File('uploaded_files/0.png');
  await part.pipe(file.openWrite());
}

I made a gist with the working server: https://gist.github.com/lslv1243/1036364b10c6578d969cb4ed2d7eba42

NOTE: on the gist I changed the path from /save_screenshot to /screenshot