graphicbeacon/main.dart

## main.dart
// bin/main.dart

import 'dart:io';

import 'package:mime/mime.dart';

main() async {
  var server = await HttpServer.bind('localhost', 8085);

  server.listen((request) async {
    if (request.uri.path != '/fileupload') {
      request.response
        ..headers.contentType = ContentType.html
        ..write('''
          <html>
          <head>
            <title>Image Upload Server</title>
          </head>
          <body>
            <form method="post" action="/fileupload" enctype="multipart/form-data">
              <input type="file" name="fileupload" /><br /><br />
              <button type="submit">Upload to server</button>
            </form>
          </body>
          </html>
        ''');
    } else {
      // accessing /fileupload endpoint
      List<int> dataBytes = [];

      await for (var data in request) {
        dataBytes.addAll(data);
      }

      String boundary = request.headers.contentType.parameters['boundary'];
      final transformer = MimeMultipartTransformer(boundary);
      final uploadDirectory = './upload';

      final bodyStream = Stream.fromIterable([dataBytes]);
      final parts = await transformer.bind(bodyStream).toList();

      for (var part in parts) {
        print(part.headers);
        final contentDisposition = part.headers['content-disposition'];
        final filename = RegExp(r'filename="([^"]*)"')
            .firstMatch(contentDisposition)
            .group(1);
        final content = await part.toList();

        if (!Directory(uploadDirectory).existsSync()) {
          await Directory(uploadDirectory).create();
        }

        await File('$uploadDirectory/$filename').writeAsBytes(content[0]);
      }
    }

    await request.response.close();
  });
}

## pubspec.yaml
name: image_upload_server
description: A sample command-line application.
version: 1.0.0
homepage: https://www.creativebracket.com
author: Jermaine Oppong

environment:
  sdk: '>=2.5.0 <3.0.0'

dependencies:
  path: ^1.6.0
  mime: ^0.9.6+3 # We need this package here.

dev_dependencies:
  pedantic: ^1.8.0
  test: ^1.6.0
	// bin/main.dart

	import 'dart:io';

	import 'package:mime/mime.dart';

	main() async {
	var server = await HttpServer.bind('localhost', 8085);

	server.listen((request) async {
	if (request.uri.path != '/fileupload') {
	request.response
	..headers.contentType = ContentType.html
	..write('''
	<html>
	<head>
	<title>Image Upload Server</title>
	</head>
	<body>
	<form method="post" action="/fileupload" enctype="multipart/form-data">
	<input type="file" name="fileupload" /><br /><br />
	<button type="submit">Upload to server</button>
	</form>
	</body>
	</html>
	''');
	} else {
	// accessing /fileupload endpoint
	List<int> dataBytes = [];

	await for (var data in request) {
	dataBytes.addAll(data);
	}

	String boundary = request.headers.contentType.parameters['boundary'];
	final transformer = MimeMultipartTransformer(boundary);
	final uploadDirectory = './upload';

	final bodyStream = Stream.fromIterable([dataBytes]);
	final parts = await transformer.bind(bodyStream).toList();

	for (var part in parts) {
	print(part.headers);
	final contentDisposition = part.headers['content-disposition'];
	final filename = RegExp(r'filename="([^"]*)"')
	.firstMatch(contentDisposition)
	.group(1);
	final content = await part.toList();

	if (!Directory(uploadDirectory).existsSync()) {
	await Directory(uploadDirectory).create();
	}

	await File('$uploadDirectory/$filename').writeAsBytes(content[0]);
	}
	}

	await request.response.close();
	});
	}
	name: image_upload_server
	description: A sample command-line application.
	version: 1.0.0
	homepage: https://www.creativebracket.com
	author: Jermaine Oppong

	environment:
	sdk: '>=2.5.0 <3.0.0'

	dependencies:
	path: ^1.6.0
	mime: ^0.9.6+3 # We need this package here.

	dev_dependencies:
	pedantic: ^1.8.0
	test: ^1.6.0