WSAECONNRESET An existing connection was forcibly closed by the remote host.

Explains the meaning of the "WSAECONNRESET An existing connection was forcibly closed by the remote host." error and demonstrates a way to reproduce it by setting the "No Transfer Timeout" setting on a FileZilla FTP server to a very small value.

Download: Chilkat .NET Assemblies

Chilkat.Ftp2 ftp = new Chilkat.Ftp2();

bool success;

//  Any string unlocks the component for the 1st 30-days.
success = ftp.UnlockComponent("Anything for 30-day trial");
if (success != true) {
    MessageBox.Show(ftp.LastErrorText);
    return;
}

ftp.Hostname = "192.168.1.108";
ftp.Username = "myLogin";
ftp.Password = "myPassword";

//  Connect and login to the FTP server.
success = ftp.Connect();
if (success != true) {
    MessageBox.Show(ftp.LastErrorText);
    return;
}

ftp.Passive = true;

//  In this example, we've set the FileZilla FTP Server's
//  "No Transfer Timeout" to 5 seconds.  This is a setting
//  on the FTP server (not in the Chilkat FTP component).
//  It causes the server to disconnect from the client after
//  5 seconds of no upload or download activity.  As you'll see,
//  sending commands over the control channel, such as
//  NOOP (no-operation) commands will have no effect.
//  It is an upload, download, or directory listing that is required.

//  This code will wait 10 seconds before proceeding with
//  the PutFile.  This should be enough time for the FileZilla
//  server to disconnect.
int i;
for (i = 0; i <= 10; i++) {
    //  Sleep for 1 second
    ftp.SleepMs(1000);

    //  Send a NOOP command to the FTP server.
    //  After about 5 iterations, it should fail and the LastErrorText
    //  will contain this message:
    //  WSAECONNRESET An existing connection was forcibly closed by the remote host.
    success = ftp.Noop();
    if (success != true) {
        textBox1.Text += ftp.LastErrorText + "\r\n";
        break;
    }

}

//  What happens if we try to upload a file without an existing
//  connection?
//  Let's do it and find out...

//  Upload a file.
string localFilename;
localFilename = "c:/temp/hamlet.xml";
string remoteFilename;
remoteFilename = "hamlet.xml";

success = ftp.PutFile(localFilename,remoteFilename);
if (success != true) {

    //  In Active mode (i.e. non-passive), we get this error:
    //  "Failed to get socket's IP address. Socket may already be disconnected."
    //  In Passive mode, we'll get this error:
    //  " No socket exists for sending (2)"
    textBox1.Text += ftp.LastErrorText + "\r\n";
    return;
}

ftp.Disconnect();

MessageBox.Show("File Uploaded!");