FTP Error The remote server returned an error: 150 Opening data channel for file download

Question

I have an FTPS site I need to connect to and get a file from. A vendor will be dropping a csv file there daily and I have to retrieve it and process it. My problem is no matter what I try and I can't connect to this site. I realize FTPS is different than SFTP and according to my research my normal method of getting files from FTP should work simply by adding an EnableSsl flag as seen below (ip, port, credentials have been changed obviously):

string uri = "ftp://127.0.0.1:123/";
string filename = "remoteFile.txt";
uri += filename;

var request = (FtpWebRequest)WebRequest.Create(uri);
request.Credentials = new NetworkCredential("user1", "secure-password1");
request.EnableSsl = true;
request.KeepAlive = false;
request.UseBinary = true;
request.UsePassive = true;

ServicePointManager.ServerCertificateValidationCallback = (s, certificate, chain, sslPolicyErrors) => true;

request.Method = WebRequestMethods.Ftp.DownloadFile;

var response = (FtpWebResponse)request.GetResponse();   //<-- error here

Stream responseStream = response.GetResponseStream();
var reader = new StreamReader(responseStream);
var fileContents = reader.ReadToEnd();

reader.Close();
response.Close();

string filePath = @"C:\Temp\localFile.txt";
using var stream = new StreamWriter(filePath);
{
    stream.Write(fileContents);
}

I've tried variations of the 4 booleans I set on the request object. In this configuration I get the error in the title. If I switch passive to false I get a timeout. I can connect to this FTP site using WinSCP. There is a certificate on the site and I imported my connection configuration from a co-worker. There is an SHA-1 fingerprint.

I have also tried creating a connection with the WinSCP Nuget package and followed their example, I just can't seem to get the fingerprint correct:

var options = new SessionOptions
{
    Protocol = Protocol.Ftp,
    HostName = "ftp://127.0.0.1:21/",
    UserName = "user1",
    Password = "secure-password1",
    SshHostKeyFingerprint = "???",
};

using var session = new WinSCP.Session();
session.Open(options);

No matter what I've tried in that finger print property it doesn't match the pattern they want and I can't find a good example of what it should look like. On the WinSCP page it says to obtain the fingerprint from your administrator, ours provided a certificate file that has an RSA section and a Certificate section. I've tried assigning the whole file to that field, the RSA section, certificate, nothing works. I tried the fingerprint displayed in my working session from WinSCP and that doesn't work.

I've found a few questions on this site with this error but all seem to point to server issues. I figure if I can connect and get files using WinSCP then I should be able to do it through code as well.

thanks

Zoey Zoey · Accepted Answer · 2020-10-08T17:33:32

As Martin suggested I opened WinSCP, logged into my FTP site using the app. Then I clicked the Session menu and chose Generate URL/Code... Click the .NET assembly code tab at the top and pasted the code into my project

// Set up session options
SessionOptions sessionOptions = new SessionOptions
{
    Protocol = Protocol.Ftp,
    HostName = "127.0.0.1",
    PortNumber = 21,
    UserName = "user1",
    Password = "secure-password1",
    FtpSecure = FtpSecure.Explicit,
    TlsHostCertificateFingerprint = "2f:f5:ab:e5:f7:27:65:12:30:73:3d:9a:b7:12:88:11:62:0e:6f:a1",
};

using (Session session = new Session())
{
    // Connect
    session.Open(sessionOptions);

    // Your code
}

I hope this helps whoever is stuck on this like I was.

FTP Error The remote server returned an error: 150 Opening data channel for file download

1 Answers