连接不一致，将文件从Azure上传到Amazon SFTP站点（WinSCP）

Question

I have searched the StackOverflow site for this specific issue, but no luck. There are items close, but nothing quite handles my issue.

I have a C# application which uses the latest WinSCP (5.7.5) Nuget. The application is running on an Azure server, and trying to upload multiple files to an Amazon SFTP site.

For testing, I send 3 files, with a new connection for each. I typically get 1 out of 3 connected and sent immediately and successfully, the other two pause for around 10 seconds and give me a Connection Time Out error. Note that it seems to ignore the timeout setting.

If I run the same application locally, (not in Azure), it runs consistently every time.

Any ideas? I don't really have access to the Amazon FTP site to change settings or anything. I have tried Passive/Non-Passive mode and disabled the firewall on my Azure server.

    WinSCP.SessionRemoteException: Network error: Connection to "xxx-xx-xxx-xx-xxx.c
    ompute-1.amazonaws.com" timed out.
       at WinSCP.SessionLogReader.Read(LogReadFlags flags)
       at WinSCP.ElementLogReader.Read(LogReadFlags flags)
       at WinSCP.SessionElementLogReader.Read(LogReadFlags flags)
       at WinSCP.CustomLogReader.TryWaitForNonEmptyElement(String localName, LogRead
    Flags flags)
       at WinSCP.CustomLogReader.WaitForGroupAndCreateLogReader()
       at WinSCP.Session.Open(SessionOptions sessionOptions)
       at FTPTesting.Program.FtpFiles(String file, String destination) in c:\_git\as
    setbook.joel_sandbox\FTPTesting\Program.cs:line 47

Answer 1

Well guys, I did some more testing. Just out of curiosity I spun up a nearly identical Azure machine, and moved my FTP application to it.

No errors at all. It ran for hours with no messages. I kept it running on the first bad Azure machine as well, and it was still generating intermittent errors.

I don't quite know how azure resources are allocated, but the error continued on the old machine, even after stopping and starting the machine. The new machine never threw error an error...

I kept both machines running overnight. And after a while the old machine quit throwing errors, and hasn't thrown an error since. Could it be self-healing or something, after having errors for such a long time?

I'd been dealing with the intermittent errors for weeks, so it wasn't just something funny yesterday.