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An FTP secure client library for C#

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10 Dec 2008CPOL2 min read 490K   15.8K   135   106
How to implement an FTP secure connection with an SSL stream class.

Introduction

The purpose of this article is to create a C # FTP client in Secure mode, so if you don’t have much knowledge of FTPS, I advise you to take a look at this: FTPS.

In the .NET Framework, to upload a file in FTPS mode, we generally use the FtpWebRequest class, but you can not send commands with « quote » arguments, and even if you search on the web, you will not find a concrete example of a secured C# FTP client.

It’s for those reasons I decided to create this article.

SSL Stream?

To send a socket in Secure Socket Layer (SSL) mode, we use the class System.Net.Security.SslStream.

Provides a stream used for client-server communication that uses the Secure Socket Layer (SSL) security protocol to authenticate the server and optionally the client”.

For more information, refer to MSDN.

Using the Code

1. Pre-Authenticate

C#
FTPFactory ftp = new FTPFactory();
ftp.setDebug(true);
ftp.setRemoteHost(Settings.Default.TargetFtpSource);

//Connect to SSL Port (990)
ftp.setRemotePort(990);
ftp.loginWithoutUser();

//Send "AUTH SSL" Command
string cmd = "AUTH SSL";
ftp.sendCommand(cmd);

Before connecting to the FTP server in SSL mode, you have to define the 990 SSL port and send the « AUTH SSL » command authentication using SSL.

WelcomeFTPSecure.JPG

2. Create SSL Stream

C#
//Create SSL Stream
ftp.getSslStream();
ftp.setUseStream(true);
//Login to FTP Secure
ftp.setRemoteUser(Settings.Default.TargetFtpSecureUser);
ftp.setRemotePass(Settings.Default.TargetFtpSecurePass);
ftp.login();

ftp.getSslStream() creates an SSL stream from client socket which will be used for exchange between the client and the server FTPS. Then, you have to enter a login and password to authenticate on the FTPS server.

Note: if the SSL stream is well established, then I display all the information about the server certificate.

CertificatInfos.JPG

3. Upload File

C#
//Set ASCII Mode
ftp.setBinaryMode(false);

//Send Arguments if you want
//cmd = "site arg1 arg2";
//ftp.sendCommand(cmd);

//Upload file
ftp.uploadSecure(@"Filepath", false);

ftp.close();

Before uploading a file, you have to specify the mode: ftp.setBinaryMode(bool value).

  • value is false --> ASCII mode
  • value is true --> Binary mode

By default, it’s binary. Now, you upload the file using:

C#
ftp.uploadSecure(@"Filepath", false)

Note: you can upload in non secured mode using ftp.upload().

Points of Interest

I learned how an SSL stream and the RAW FTP communication works between a client and an FTP server. Searching on the web, I found many who were stuck on the issue of SSL communication with an FTP server, so I hope this article will be of great help.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


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Comments and Discussions

 
GeneralRe: Getting a file listing returning odd characters Pin
Member 1044694019-Jan-14 23:57
Member 1044694019-Jan-14 23:57 
GeneralDuring PASV I get: 500 You need to use a client supporting PRET (PRE Transfer) to use PASV Pin
AndreasLink14-Nov-09 3:56
AndreasLink14-Nov-09 3:56 
GeneralRe: During PASV I get: 500 You need to use a client supporting PRET (PRE Transfer) to use PASV Pin
AndreasLink14-Nov-09 4:23
AndreasLink14-Nov-09 4:23 
GeneralCode hangs up on readReply() Pin
Ericc196928-Oct-09 15:57
Ericc196928-Oct-09 15:57 
GeneralRe: Code hangs up on readReply() Pin
AndreasLink14-Nov-09 4:00
AndreasLink14-Nov-09 4:00 
GeneralRe: Code hangs up on readReply() Pin
Member 3728808-Dec-09 9:54
Member 3728808-Dec-09 9:54 
GeneralRe: Code hangs up on readReply() Pin
MagicPT13-Jan-10 6:46
MagicPT13-Jan-10 6:46 
GeneralRe: Code hangs up on readReply() [modified] Pin
Silve_X17-Jul-10 23:52
Silve_X17-Jul-10 23:52 
Maybe this answer is a bit late, but it might be a little help for others.
While looping through the readLine() void, the mes might get bigger and the "220 " line might never be reached.
I added two lines to the code to make sure it doesn't get flooded.

I mean here:

private string readLine()
{
bytes = 0; //Reset bytes to zero because of the looping through this entire void when the needed line is not received yet.
mes = string.Empty; //Reset mes to empty string because of the looping through this entire void when the needed line is not received yet.

while(true)
{
if (useStream)
bytes = stream.Read(buffer, buffer.Length, 0);
else
bytes = clientSocket.Receive(buffer, buffer.Length, 0);


mes += ASCII.GetString(buffer, 0, bytes);
if(bytes < buffer.Length)
{
break;
}
}
....

Whether this is correct I don't know, however it works for me.

modified on Monday, July 19, 2010 2:59 AM

GeneralError on port=990 Pin
ZoyaKhan1825-Sep-09 9:37
ZoyaKhan1825-Sep-09 9:37 
GeneralRe: Error on port=990 Pin
kadaoui el mehdi25-Sep-09 9:46
kadaoui el mehdi25-Sep-09 9:46 
GeneralMessage Closed Pin
25-Sep-09 10:02
ZoyaKhan1825-Sep-09 10:02 
GeneralRe: Error on port=990 Pin
kadaoui el mehdi25-Sep-09 10:04
kadaoui el mehdi25-Sep-09 10:04 
GeneralRe: Error on port=990 Pin
SonnyDude13-Jul-10 21:13
SonnyDude13-Jul-10 21:13 
GeneralRe: Error on port=990 Pin
mendick200016-Nov-10 4:49
mendick200016-Nov-10 4:49 
GeneralRe: Error on port=990 Pin
maximus.dec.meridius9-Mar-11 5:11
maximus.dec.meridius9-Mar-11 5:11 
Answer(Solution) The code hang on the function AuthenticateAsClient of the data stream. Pin
sonnguyen7917-Jul-09 12:48
sonnguyen7917-Jul-09 12:48 
GeneralRe: (Solution) The code hang on the function AuthenticateAsClient of the data stream. Pin
Kris Munroe22-Sep-09 8:13
Kris Munroe22-Sep-09 8:13 
AnswerRe: (Solution) The code hang on the function AuthenticateAsClient of the data stream. Pin
Jonathan.wilkins28-Jan-10 21:37
Jonathan.wilkins28-Jan-10 21:37 
GeneralRe: (Solution) The code hang on the function AuthenticateAsClient of the data stream. Pin
Member 1379384125-Apr-18 10:02
Member 1379384125-Apr-18 10:02 
GeneralRe: (Solution) The code hang on the function AuthenticateAsClient of the data stream. Pin
Member 1288800424-Sep-19 4:25
Member 1288800424-Sep-19 4:25 
GeneralRe: (Solution) The code hang on the function AuthenticateAsClient of the data stream. Pin
Member 383304120-Oct-09 12:16
Member 383304120-Oct-09 12:16 
QuestionUsing the lib to connect a non secure ftp server Pin
david_864015-Jul-09 2:33
david_864015-Jul-09 2:33 
QuestionFTP Client and Server Pin
aschreiber25-Jun-09 13:10
aschreiber25-Jun-09 13:10 
GeneralNotImplementedException Pin
SimpleData6-May-09 2:10
SimpleData6-May-09 2:10 
GeneralExplicit mode Pin
adhager21-Apr-09 18:16
adhager21-Apr-09 18:16 

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