As a developer, you will have the opportunity to transfer files, such as Excel, CVS, Images, and flat files, to third-party or upstream/downstream systems.
There are different ways to transfer.
Different ways to transfer
- Transfer through the SFTP client through an open-source package
- File copy method using service account
What are the methods in the open-source package?
- Secure File Transfer Protocols
- Cloud-Based File Sharing
- API’s and Webhooks
- Managed File Transfer (MFT)
- Email with Encryption
- VPN + Network shares
- Message Queues or Middleware
In this blog, I will explain the use case and practical implementation of a widely used open-source API for automated, secure file transfers.
Transfer through the SFTP client through an open-source package- SSH.NET
We have popular packages such as SSH.NET, WinSCP.NET, SharpSSH & etc.
In my point of view, for open-source and .NET Core compatibility, SSH.NET is the best choice. It’s lightweight, actively used, and works well for most SFTP needs.
Let’s go for practical implementation
Install NuGet Package: Install-Package SSH.NET
Reference: https://www.nuget.org/packages/ssh.net/
Authentication Method Options
- Private Key Authentication Method
- Password Authentication Method
- Keyboard Interactive Authentication Method
Private Key Authentication Method
using Renci.SshNet;
using System.Text;
//Private key
var key = System.IO.File.ReadAllText("privatekey.ppk");
//sftp_host
var sftp_host = "sftp_server";
//sftp_user
var sftp_username = "sftpuser";
//file to transfer
var file = "C:\\Users\\test.txt";
//sftp_folder directory
var sftp_folderpath = "/appl/data/inbound";
var buf = new MemoryStream(Encoding.UTF8.GetBytes(key));
var privateKeyFile = new PrivateKeyFile(buf);
// Attach the private key while making connection
var connectionInfo = new ConnectionInfo(sftp_host, sftp_username,
new PrivateKeyAuthenticationMethod(sftp_username, privateKeyFile));
//Connect through Port ( Default Port is 22 )
/*
var connectionbyPort = new
ConnectionInfo
( string host,
int port,
string username,
params AuthenticationMethod[] authenticationMethods
);
*/
//Connect through Proxy ( HTTP, SOCKS4, SOCKS5 ).
/*
* proxyType: Enum ProxyTypes.
proxyHost, proxyPort, proxyUsername, proxyPassword: Proxy details.
var connectionbyPort = new ConnectionInfo(
string host,
int port,
string username,
ProxyTypes proxyType,
string proxyHost,
int proxyPort,
string proxyUsername,
string proxyPassword,
params AuthenticationMethod[] authenticationMethods);
*/
using (var client = new SftpClient(connectionInfo))
{
try
{
using (FileStream fs = System.IO.File.Open(file, FileMode.Open))
{
client.Connect();
client.UploadFile(fs, sftp_folderpath+ Path.GetFileName(file), null);
client.Disconnect();
}
}
catch (Exception ex)
{
if (client.IsConnected)
client.Disconnect();
}
}
Password Authentication Method
string username = "your-username";
string password = "your-password";
//sftp_host
var host = "sftp_server";
int port = 22;
//file to transfer
var file = "C:\\Users\\test.txt";
//sftp_folder directory
var sftp_folderpath = "/appl/data/inbound";
using (var client = new SshClient(host,port,username,password))
{
try
{
if(sftp.IsConnected)
{
client.Connect();
Console.WriteLine("Connected successfully!");
using (FileStream fs = System.IO.File.Open(file, FileMode.Open))
{
client.Connect();
client.UploadFile(fs, sftp_folderpath + Path.GetFileName(file), null);
client.Disconnect();
}
}
}
catch (Exception ex)
{
if (client.IsConnected)
client.Disconnect();
}
}
Keyboard Interactive Authentication Method
string username = "your-username";
string password = "your-password";
//sftp_host
var host = "sftp_server";
int port = 22;
//file to transfer
var file = "C:\\Users\\test.txt";
//sftp_folder directory
var sftp_folderpath = "/appl/data/inbound";
// Define the keyboard-interactive authentication method
var keyboardAuth = new KeyboardInteractiveAuthenticationMethod(username);
// Handle the interactive prompts
keyboardAuth.AuthenticationPrompt += (sender, e) =>
{
foreach (var prompt in e .Prompts)
{
Console.WriteLine($"Prompt: {prompt.Request}");
// Automatically respond if the prompt contains 'Password'
if (prompt.Request.ToLower().Contains("password"))
{
prompt.Response = password;
}
// You could add logic here to handle OTP or verification codes
// else if (prompt.Request.ToLower().Contains("verification code"))
// {
// prompt.Response = "123456"; // Example for OTP
// }
}
};
// Optionally add password-based auth fallback
var passwordAuth = new PasswordAuthenticationMethod(username, password);
// Combine both authentication methods
var connectionInfo = new ConnectionInfo(
host,
port,
username,
passwordAuth,
keyboardAuth
);
//Transfer file using connection
using (var client = new SftpClient(connectionInfo))
{
try
{
using (FileStream fs = System.IO.File.Open(file, FileMode.Open))
{
client.Connect();
client.UploadFile(fs, sftp_folderpath+ Path.GetFileName(file), null);
client.Disconnect();
}
}
catch (Exception ex)
{
if (client.IsConnected)
client.Disconnect();
}
}
File copy method using service account
This approach provides a simple way to transfer files, provided the target system permits creating a service account.
To implement it, create a service account user (similar to a regular user account) and grant it read/write access to the target directory.
//file to transfer
var source = "C:\\Users\\test.txt";
//sftp_folder directory
var target = "/appl/data/inbound";
File.Copy(source, target);
While deploying the solution into the server, you need to log on with this service account user
Windows service logon through a service account user
For Example, in Windows Server - Services ( “services.msc”), we need to log on to that service by using username & password.
In IIS
In Project – Advanced settings – Physical path credentials – Log on with user name & password.
as it is less code-intensive and relies solely on.
Summary
Based on my professional experience, I would say the file copy method is the best way to transfer, which is a less code-intensive implementation, and relies only on the network transfer.
Hope you enjoyed the article!!!