How to send arbitrary FTP commands in C#

Question

I have implemented the ability to upload, download, delete, etc. using the FtpWebRequest class in C#. That is fairly straight forward.

What I need to d

Answer 1

The FtpWebRequest won't help you as Thomas Levesque has said in his answer. You can use some third party solutions or the following, simplified TcpClient based code which I have refactored from an answer written in Visual Basic:

public static void SendFtpCommand()
{
    var serverName = "[FTP_SERVER_NAME]";
    var port = 21;
    var userName = "[FTP_USER_NAME]";
    var password = "[FTP_PASSWORD]"
    var command = "SITE CHMOD 755 [FTP_FILE_PATH]";

    var tcpClient = new TcpClient();
    try
    {
        tcpClient.Connect(serverName, port);
        Flush(tcpClient);

        var response = TransmitCommand(tcpClient, "user " + userName);
        if (response.IndexOf("331", StringComparison.OrdinalIgnoreCase) < 0)
            throw new Exception(string.Format("Error \"{0}\" while sending user name \"{1}\".", response, userName));

        response = TransmitCommand(tcpClient, "pass " + password);
        if (response.IndexOf("230", StringComparison.OrdinalIgnoreCase) < 0)
            throw new Exception(string.Format("Error \"{0}\" while sending password.", response));

        response = TransmitCommand(tcpClient, command);
        if (response.IndexOf("200", StringComparison.OrdinalIgnoreCase) < 0)
            throw new Exception(string.Format("Error \"{0}\" while sending command \"{1}\".", response, command));
    }
    finally
    {
        if (tcpClient.Connected)
            tcpClient.Close();
    }
}

private static string TransmitCommand(TcpClient tcpClient, string cmd)
{
    var networkStream = tcpClient.GetStream();
    if (!networkStream.CanWrite || !networkStream.CanRead)
        return string.Empty;

    var sendBytes = Encoding.ASCII.GetBytes(cmd + "\r\n");
    networkStream.Write(sendBytes, 0, sendBytes.Length);

    var streamReader = new StreamReader(networkStream);
    return streamReader.ReadLine();
}

private static string Flush(TcpClient tcpClient)
{
    try
    {
        var networkStream = tcpClient.GetStream();
        if (!networkStream.CanWrite || !networkStream.CanRead)
            return string.Empty;

        var receiveBytes = new byte[tcpClient.ReceiveBufferSize];
        networkStream.ReadTimeout = 10000;
        networkStream.Read(receiveBytes, 0, tcpClient.ReceiveBufferSize);

        return Encoding.ASCII.GetString(receiveBytes);
    }
    catch
    {
        // Ignore all irrelevant exceptions
    }

    return string.Empty;
}

You can expect the following flow while getting through the FTP:

220 (vsFTPd 2.2.2)
user [FTP_USER_NAME]
331 Please specify the password.
pass [FTP_PASSWORD]
230 Login successful.
SITE CHMOD 755 [FTP_FILE_PATH]
200 SITE CHMOD command ok.