FTP Upload Issue After Updating to .Net Core 3.1

[d-daniel-de-sousa]

Issue Title

FTP Upload Issue After Updating to .Net Core 3.1

General

Version: .Net Core 3.1
OS: Windows
Solution Deployed: Web App Azure
Using Swagger.
Vnet

After Updating the Net Core Version from 2.1 to 3.1 the method to upload a file just stop working after deployed on Azure Web App.

If I Deploy it with a later version (2.1) it starts to work again.

Exception/error

Exception thrown: 'System.Net.WebException' in System.Net.Requests.dll
Unable to connect to remote server

Code

        public async Task<string> UploadFileFTP(string file)
        {
             FtpConfig ftpConfig = LightConfigurator.Config<FtpConfig>("FtpConfig");           

            FileInfo fileInfo = new FileInfo(file);
            Uri serverUri = new Uri(ftpConfig.Server + ":" + ftpConfig.Port + ftpConfig.Folder + fileInfo.Name);
            FtpWebRequest request = (FtpWebRequest)WebRequest.Create(serverUri);
            request.Method = WebRequestMethods.Ftp.UploadFile;
            request.Credentials = new NetworkCredential(ftpConfig.User, ftpConfig.Password);
            request.Proxy = null;
            request.UseBinary = true;
            request.ContentLength = fileInfo.Length;
            using (FileStream fs = fileInfo.OpenRead())
            {
                byte[] buffer = new byte[2048];
                int bytesSent = 0;
                int bytes = 0;
                using (Stream stream = request.GetRequestStream())
                {
                    while (bytesSent < fileInfo.Length)
                    {
                        bytes = fs.Read(buffer, 0, buffer.Length);
                        stream.Write(buffer, 0, bytes);
                        bytesSent += bytes;
                    }
                }
            }

            RegisterEvents.Register(ActionEnum.FPT_UPLOADING, "UploadFileFTP", $"Concluída a subida no FTP.");

            return "success";
        }

[scalablecory]

Can you confirm the server is up and responding? It seems like it can't connect.

Do you know if the same happens in .NET 5?

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Issue Details

---

Issue Title

FTP Upload Issue After Updating to .Net Core 3.1

General

Version: .Net Core 3.1
OS: Windows
Solution Deployed: Web App Azure
Using Swagger.
Vnet

After Updating the Net Core Version from 2.1 to 3.1 the method to upload a file just stop working after deployed on Azure Web App.

If I Deploy it with a later version (2.1) it starts to work again.

Exception/error

Exception thrown: 'System.Net.WebException' in System.Net.Requests.dll
Unable to connect to remote server

Code

    public async Task<string> UploadFileFTP(string file)
    {
         FtpConfig ftpConfig = LightConfigurator.Config<FtpConfig>("FtpConfig");           

        FileInfo fileInfo = new FileInfo(file);
        Uri serverUri = new Uri(ftpConfig.Server + ":" + ftpConfig.Port + ftpConfig.Folder + fileInfo.Name);
        FtpWebRequest request = (FtpWebRequest)WebRequest.Create(serverUri);
        request.Method = WebRequestMethods.Ftp.UploadFile;
        request.Credentials = new NetworkCredential(ftpConfig.User, ftpConfig.Password);
        request.Proxy = null;
        request.UseBinary = true;
        request.ContentLength = fileInfo.Length;
        using (FileStream fs = fileInfo.OpenRead())
        {
            byte[] buffer = new byte[2048];
            int bytesSent = 0;
            int bytes = 0;
            using (Stream stream = request.GetRequestStream())
            {
                while (bytesSent < fileInfo.Length)
                {
                    bytes = fs.Read(buffer, 0, buffer.Length);
                    stream.Write(buffer, 0, bytes);
                    bytesSent += bytes;
                }
            }
        }

        RegisterEvents.Register(ActionEnum.FPT_UPLOADING, "UploadFileFTP", $"Concluída a subida no FTP.");

        return "success";
    }

Author:	d-daniel-de-sousa
Assignees:	-
Labels:	area-System.Net, untriaged
Milestone:	-

[wfurt]

I think we switched to dual mode sockets in 3.x @scalablecory. This feels like dup of #44686.
I would suggest too try it with the WEBSITE_VNET_SUPPORT_DUAL_STACK_SOCKETS = 1.

[karelz]

@wfurt the linked bug is regression between 3.1 and 5.0. This report is about regression between 2.1 and 3.1, so it won't be likely the same.

Are you able to minimize the repro (ideally HelloWorld style) such that we can try it ourselves as well?
Is your problem specific to Azure WebApps deploymnet? Or are you able to reproduce it also locally?

[wfurt]

this is because HTTP switched to dual mode socket in 5.0. Same happened to TcpClient in 3.0 and that impacted FTP in 3.0 as well. Can you reproduce it outside of VNET @d-daniel-de-sousa?

[karelz]

Triage: Seems to be Azure Web Apps problem, which should be shortly fixed. Closing.