C# Program gets stuck in FtpWebResponse after server disconnects

Question

I have a C# program that checks a ftp directory for new files every x seconds. If a new file is found it is downloaded. That works fine. If I start the program without running the ftp server the program loops and returns a message that the server cannot be reached. Then I start the server and the program connects as it should. But if I quit the ftp server again my program gets stuck in the FtpWebResponse.

I have a using statement block in a try catch block to close all connections.

while (true)
{
    //...
    FtpFileList = null;
    while (FtpFileList == null)
    {
        FtpFileList = await GetFtpFileList(adress, user, password);
        await Task.Delay(3000);
    }
    await Task.Delay(27000);
    //...
}


public static async Task<List<string>> GetFtpFileList(string address, string user, string password)
{
    try
    {
        List<string> returnValue = new List<string>();
        FtpWebRequest request = (FtpWebRequest)WebRequest.Create(address);
        request.Method = WebRequestMethods.Ftp.ListDirectory;
        request.Credentials = new NetworkCredential(user, password);
        using (FtpWebResponse response = (FtpWebResponse)await request.GetResponseAsync()) //The program gets stuck here
        {
            Stream responseStream = response.GetResponseStream();
            StreamReader reader = new StreamReader(responseStream);
            while (reader.Peek() >= 0)
            {
                returnValue.Add(reader.ReadLine());
            }
        }
        AddToLogFile(DateTime.Now + ": " + "FTP directory updated");
        return returnValue;
    }
    catch (WebException e)
    {
        AddToLogFile(DateTime.Now + ": " + e.Message);
        return null;
    }
}

I expect the program to reconnect to the server after the connection was lost but instead it gets stuck.

Any help and hints how to solve that issue is appreciated.

Answer 1

Just to let you know I solved the issue by implementing a workaround: Instead of using await request.GetResponseAsync() I use the normal GetResponse() method in another thread which works without any problems so far: await Task.Run(() => request.GetResponse())