C# Error in SFTP connection. Exception: System.Net.Sockets.SocketException (11001): No such host is known

Question

I have written a SFTP connection, which is connecting to a secure domain host (MBox location) in .NET Core:

IPHostEntry ip = Dns.GetHostEntry(Host);

using (SftpClient client = new SftpClient(ip.ToString(), Port, User, Password))
{
    //connect to client
    client.Connect();
    var files = client.ListDirectory(PathToRead).ToList();
    ......
    //wait for downloads to finish
    await Task.WhenAll(tasks);

    // disconnect the client by closing connection
    client.Disconnect();
}

which is hosted in Azure App service with subscription and Azure AD configured as per my client's domain. When I am running the code I am seeing the following error:

Error in FTP connection. Exception: System.Net.Sockets.SocketException (11001): No such host is known

Can you please help.

Derrick Moeller · Accepted Answer · 2020-03-17 20:08:30Z

1

ip.ToString() returns the name of the type, System.Net.IPHostEntry. Your SftpClient is then trying to look up System.Net.IPHostEntry in DNS and not finding anything, thus the exception.

I'm not familiar with the constructors provided by SftpClient, but presumably you need to do something like:

using (SftpClient client = new SftpClient(ip.AddressList, Port, User, Password))

answered Mar 17, 2020 at 20:08

Derrick Moeller

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2 Comments

Martin Prikryl Over a year ago

Or simply new SftpClient(Host, Port, User, Password).

aniban Over a year ago

sorry guys, nothing is working, I think, I have to append the sFTP host IP with domain white-list, still searching

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