The Solution in short:

App Service running .Net App
Always on is set to On.

The App are Downloading file and fileinfo from Ftp server using WinSCP in the C# code.

From Log file:
"A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond."

It seems to fail at the code part:

var sessionOptions = new SessionOptions()
{
Protocol = Protocol.Ftp,
HostName = _hostName,
UserName = _userName,
Password = _password,
TimeoutInMilliseconds = 60000,
};
_session = new Session();
_session.DisableVersionCheck = true;
_session.DebugLogLevel = 0;
_session.ExecutablePath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory + "winscp.exe");
_session.Open(sessionOptions)


The error only occurs when vi run the App on Azure, I cannot recreate the error in Debug on my local machine. If I debug the App local, it seems to get the production App on Azure to start running.


I do not know if I have to change the WinSCP settings in the code, or I should change the settings in Azure App Service.