AWS S3 File Upload .NET SDK (.NET Core) Unable to write data to the transport connection

Question

I'm writing a function to upload multiple files to AWS S3. Even with a single file, the commented code using TransferUtilityUploadRequest below fails with an error:

System.IO.IOException: Unable to write data to the transport connection: An existing connection was forcibly closed by the remote host.

The uncommented code works, (but I am unable to set ACL permissions). Having looked at several examples online, I am not sure what I am doing wrong? The RequestFormLimits are not this issue here, the code fails at the point it tries to upload to S3.

    [HttpPost("test/raw-file-upload-s3")]
[RequestFormLimits(MultipartBodyLengthLimit = 1073741824)]
    [RequestSizeLimit(1073741824)]
    public async Task<ActionResult<object>> UploadFiles3(IList<IFormFile> files)
    {
        var regionEndpoint = RegionEndpoint.GetBySystemName(_awsS3RegionEndpoint);

        var uploadedFileNames = new List<string>();

        using (var awsS3Client = new AmazonS3Client(new BasicAWSCredentials(_awsAccessKeyId, _awsSecretKey), regionEndpoint))
        {
            using (var fileTransferUtility = new TransferUtility(awsS3Client))
            {
                var dateBasedDirectoryName = GetDateBasedDirectoryName();

                string contentDirectory = $@"example/";

                var tasks = new Task[files.Count];

                var streams = new Stream[files.Count];

                for (int i = 0; i < files.Count; i++)
                {
                    string fileName = $"{Guid.NewGuid()}_{files[i].FileName}";

                    string key = $"{contentDirectory}{fileName}";

                    streams[i] = files[i].OpenReadStream();

                    tasks[i] = fileTransferUtility.UploadAsync(streams[i], _awsS3AssetsBucket, key);

                    // var fileTransferUtilityRequest = new TransferUtilityUploadRequest
                    // {
                    //     BucketName = _awsS3AssetsBucket,
                    //     Key = key,
                    //     CannedACL = S3CannedACL.PublicRead,
                    //     InputStream = streams[i]
                    // };

                    // tasks[i] = fileTransferUtility.UploadAsync(fileTransferUtilityRequest);
                }

                await Task.WhenAll(tasks).ConfigureAwait(false);

                for (int i = 0; i < files.Count; i++)
                {
                    streams[i].Close();
                }
            }
        }

        return new
        {
            uploadedFiles = uploadedFileNames
        };
    }

Answer 1

Can you try below

// Set Canned ACL (PublicRead) for an existing item
client.PutACL(new PutACLRequest
{
    BucketName = _awsS3AssetsBucket,
    Key = key,
    CannedACL = S3CannedACL.PublicRead
});

Before this line

tasks[i] = fileTransferUtility.UploadAsync(streams[i], _awsS3AssetsBucket, key);