.NET Web Service/WCF是否支持SFTP服务器间文件传输？及.NET Core实现咨询

Hey there! Let's tackle your two questions about SFTP transfers in .NET:

Native .NET Web Services (ASMX) and WCF don't have built-in support for the SFTP protocol. These technologies are focused on building SOAP/REST-based services, not handling file transfer protocols like SFTP. If you want to implement cross-SFTP server transfers using these frameworks, you'll need to pair them with a third-party SFTP library. You'd encapsulate the SFTP connection, download, and upload logic within your Web Service/WCF service methods to handle the actual file movement between servers.

First off: .NET Core (and modern .NET 5+) also doesn't include native SFTP tools, but the ecosystem has excellent third-party libraries that make this straightforward. Here's the best approach to build your service:

• Pick a reliable SFTP library: The most popular and widely used option is SSH.NET — it's lightweight, fully supports .NET Core/.NET 5+, and provides a clean API for all SFTP operations (connecting, uploading, downloading, directory management, etc.). Another option is WinSCP.NET, but it requires the external WinSCP client to be installed, making SSH.NET a more self-contained choice for most scenarios.
• Encapsulate SFTP logic in reusable services: Create a dedicated service class (e.g., SftpTransferService) that handles all interactions with SFTP servers. For example, add a method like TransferFileBetweenServers that takes source server credentials, target server credentials, source file path, and target file path as parameters. This keeps your code organized and easy to test/maintain.
• Opt for streaming to avoid local file storage: For large files, don't load the entire file into memory or save it to a local temp folder. Use SSH.NET's streaming capabilities: you can directly read the file stream from the source SFTP server and pipe it into the upload stream of the target server. This saves disk space and improves transfer speed.
• Manage connections and errors properly: Always wrap SftpClient instances in using statements to ensure connections are disposed of correctly. Handle common exceptions like failed connections, missing files, or permission issues gracefully, returning clear error messages to the caller.
• Choose the right hosting model: Depending on your needs, host your transfer service as an ASP.NET Core Web API (to expose HTTP endpoints for triggering transfers) or a .NET Worker Service (to run background tasks, e.g., listening to a message queue for transfer requests). Worker Services are great for scheduled or batch transfer jobs.
• Prioritize security: Never hardcode SFTP credentials or private keys. Use .NET's configuration system with appsettings.json, Secret Manager for local development, or a secure vault (like Azure Key Vault) for production. Also, validate the SFTP server's host key to prevent man-in-the-middle attacks.

内容的提问来源于stack exchange，提问作者user1446764