Simple FTP Demo Application Using C# And .Net 2.0

Introduction

An addition to the Microsoft .NET framework 2.0 to 1.x is the support for FTP. All these days we had to rely on 3rd party libraries which pretty well suited most of our needs, but for sure, there is an extra pleasure using the .net framework library classes. The code included is not designed to be a fulfledged reusable library, but rather an easy to use and reusable pieces of code which is easily comprehensible and can be reused and tweaked to fit your specific needs. Therefore the code for each functionality(upoad, download, delete etc...) can be easy picked up separately and reused. The main motive behind this article was the unavailability of .net2.0 ftp sample codes and their usage in C#; may be because its a new entrant to the .net scenario, or the third party implementations available were working pretty well, that this area of the .net2.0 library haven't got enough focus.

Background

I started working on this FTP module as part of my official work, but the requirement soon changed and I had to do it for .net 1.1. So, I haven't travelled deeper into the rabbit hole. But I believe this gives a good, instant start for using the FTP support in .net 2.0.

Using the code

Don't forget to add the following directive:

using System.Net;
using System.IO;

The following steps can be considered as a generic procedure of getting an FTP request executed using FtpWebRequest object:

1. Create an FtpWebRequest object over an ftp server Uri
2. Set the ftp method to execute (upload, download, etc.)
3. Set options(ssl support, transfer as binary/not etc.) for the ftp webrequest.
4. Set the login credentials(username, password)
5. Execute the request.
6. Recieve the response stream(if required).
7. Close the FTP Request, in addition to any open streams.

One point to watch out while coding for any ftp application is to have the settings for the ftp request proper to suit the ftp server and its specific configurations. FtpWebRequest object exposes many poperties to have these settings in place.

The sample for the upload functionality is as follows:

First a uri is created which represents the ftp address along with the filename(directory structure included). This uri is used to create the FtpWebRequest instance.

Then properties of the FtpWebRequest object are set, which determines the settings for the ftp request.

Some of its important properties are:

• Credentials - specifies the username and password to login to the FTP server.
• KeepAlive - specifies if the control connection should be closed or not after the request is completed. By default it is set to true.
• UseBinary - denotes the datatype for file transfers. The 2 modes of file transfer in this case are Binary and ASCII. At bit level both vary in the 8th bit of a byte. ASCII uses 8th bit as insignificant bit for error control, where as, for binary all the 8 bits are significant. So take care when you go for the ASCII transmission. To be simple, all those files that open and read well in notepad are safe as ascii. Executables, formatted docs etc should be send using binary mode. BTW sending ASCII files as binary works fine most of the time.
• UsePassive - specifies to use either active or passive mode. Earlier active FTP worked fine with all clients, but now a days as most of the random ports will blocked by firewall, the active mode may fail. The passive FTP is helpful in this case. But still it causes issues at the server. The higher ports requested by client on server may also be blocked by firewall. But since FTP servers will need to make their servers accessible to the greatest number of clients, they will almost certainly need to support passive FTP. The reason why passive mode is considered safe is that, it ensures all data flow initiation comes from inside(client) the network rather than from the outside(server).
• Contentlength - setting this property is useful for the server we request to but is not of much use for us(client), because FtpWebRequest usually ignores this property value, so it will not be available for our use in most of the cases. But if we set this property, the FTP server will get an idea in advance about the size of the file it should expect(in case of upload).
• Method - Denotes what action(command) to take in the current request.(upload, download, filelist etc.) It is set a value defined in the WebRequestMethods.Ftp structure.

private void Upload(string filename)
{
    FileInfo fileInf = new FileInfo(filename);
    string uri = "ftp://" + ftpServerIP + "/" + fileInf.Name;
    FtpWebRequest reqFTP; 
    // Create FtpWebRequest object from the Uri provided
    reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + ftpServerIP + "/" + fileInf.Name)); 
    // Provide the WebPermission Credintials
    reqFTP.Credentials = new NetworkCredential(ftpUserID, ftpPassword); 
    // By default KeepAlive is true, where the control connection is not closed
    // after a command is executed.
    reqFTP.KeepAlive = false; 
    // Specify the command to be executed.
    reqFTP.Method = WebRequestMethods.Ftp.UploadFile; 
    // Specify the data transfer type.
    reqFTP.UseBinary = true; 
    // Notify the server about the size of the uploaded file
    reqFTP.ContentLength = fileInf.Length; 
    // The buffer size is set to 2kb
    int buffLength = 2048;
    byte[] buff = new byte[buffLength];
    int contentLen; 
    // Opens a file stream (System.IO.FileStream) to read the file to be uploaded
    FileStream fs = fileInf.OpenRead(); 
    try
    {
        // Stream to which the file to be upload is written
        Stream strm = reqFTP.GetRequestStream(); 
        // Read from the file stream 2kb at a time
        contentLen = fs.Read(buff, 0, buffLength); 
        // Till Stream content ends
        while (contentLen != 0)
        {
            // Write Content from the file stream to the FTP Upload Stream
            strm.Write(buff, 0, contentLen);
            contentLen = fs.Read(buff, 0, buffLength);
        } 
        // Close the file stream and the Request Stream
        strm.Close();
        fs.Close();
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message, "Upload Error");
    }
}

private void Download(string filePath, string fileName)
{
    FtpWebRequest reqFTP;
    try
    {
        //filePath = <<The full path where the file is to be created. the>>,
        //fileName = <<Name of the file to be createdNeed not name on FTP server. name name()>>
        FileStream outputStream = new FileStream(filePath + "\\" + fileName, FileMode.Create); 
        reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + ftpServerIP + "/" + fileName));
        reqFTP.Method = WebRequestMethods.Ftp.DownloadFile;
        reqFTP.UseBinary = true;
        reqFTP.Credentials = new NetworkCredential(ftpUserID, ftpPassword);
        FtpWebResponse response = (FtpWebResponse)reqFTP.GetResponse();
        Stream ftpStream = response.GetResponseStream();
        long cl = response.ContentLength;
        int bufferSize = 2048;
        int readCount;
        byte[] buffer = new byte[bufferSize];
        readCount = ftpStream.Read(buffer, 0, bufferSize);
        while (readCount > 0)
        {
            outputStream.Write(buffer, 0, readCount);
            readCount = ftpStream.Read(buffer, 0, bufferSize);
        }
        ftpStream.Close();
        outputStream.Close();
        response.Close();
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}

public string[] GetFileList()
{
    string[] downloadFiles;
    StringBuilder result = new StringBuilder();
    FtpWebRequest reqFTP;
    try
    {
        reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + ftpServerIP + "/"));
        reqFTP.UseBinary = true;
        reqFTP.Credentials = new NetworkCredential(ftpUserID, ftpPassword);
        reqFTP.Method = WebRequestMethods.Ftp.ListDirectory;
        WebResponse response = reqFTP.GetResponse();
        StreamReader reader = new StreamReader(response.GetResponseStream());
        string line = reader.ReadLine();
        while (line != null)
        {
            result.Append(line);
            result.Append("\n");
            line = reader.ReadLine();
        }
        // to remove the trailing '\n'
        result.Remove(result.ToString().LastIndexOf('\n'), 1);
        reader.Close();
        response.Close();
        return result.ToString().Split('\n');
    }
    catch (Exception ex)
    {
        System.Windows.Forms.MessageBox.Show(ex.Message);
        downloadFiles = null;
        return downloadFiles;
    }
}