Secure file transfer protocol, or SSH file transfer protocol, (SFTP) has been around for over 25 years and is still commonly used by businesses when exchanging files. SSH (Secure Shell) is used to encrypt the SFTP connection before any files are transferred, resulting in encryption of all files in transfer.
This blog post will describe an SFTP file transfer and then explain how Thru’s managed file transfer (MFT) service can be used to meet different SFTP use cases.
Servers and Clients
To use SFTP to transfer files, an SFTP client and an SFTP server are needed. So, before diving into how the transfer works, let’s quickly review some differences between a server and a client, as shown in the following table:
| Server | Client |
|---|---|
| Higher processing power | Lower processing power |
| Has resources shared by every user on the network | Used by individual users on the network |
| Stores information and fulfills requests from client | Requests information from server |
| Passive – never initiates requests | Active – always initiates requests |
| Examples: database server, file server | Examples: PCs and laptops |
How a File Transfer Between an STFP Client and an SFTP Server Works
Together, the server and client establish a request-response messaging pattern, in which one party requests the data and the other responds. The term direction of connection describes which computer initiates the connection.
Here is a high-level example of how a file transfer works when the direction of connection is from an SFTP client to an SFTP server:
- The server listens for a command for a connection on a specific port, typically the Transmission Control Protocol (TCP) port 22.
- The TCP handshake establishes the connection:
- The client sends a message (called a SYN) to the server to check its presence.
- The server sends an acknowledgement (called a SYN ACK) to the client.
- The client sends another acknowledgement message to the server.
- After the TCP handshake, the client provides credentials to authenticate the user and server.
- The file is transferred and available for download. Users may be able to see additional transfer information, including time/date, size, permissions, etc.
Learn More about SFTP
For a more detailed explanation of how SFTP works, including additional diagrams and illustrations, please see our comprehensive What Is SFTP? Guide »
Use Cases: Thru’s MFT Functions as Client or Server
Our customers have different needs and use cases, but they all appreciate the flexibility of Thru’s client/server functionality. With Thru’s MFT, you can transfer files in any server-client combination:
- Source Server Endpoint to Target Server Endpoint »
- Source Client Endpoint to Target Client Endpoint »
- Source Server Endpoint to Target Client Endpoint »
- Source Client Endpoint to Target Server Endpoint »
1. Source Server Endpoint to Target Server Endpoint
Thru pulls files from a source server endpoint and pushes them to a target server endpoint.
2. Source Client Endpoint to Target Client Endpoint
Note: In Thru, client endpoints require a FTPS/SFTP client application to authenticate, upload and download files.
The source client endpoint pushes files to Thru, then the target client endpoint pulls them.
3. Source Server Endpoint to Target Client Endpoint
Thru pulls files from a source server endpoint. Then, the target client endpoint pulls files from Thru.
4. Source Client Endpoint to Target Server Endpoint
The source client endpoint pushes files to Thru, which pushes them to a target server endpoint.
Use MFT as Client-Server Relationship for SFTP File Transfers
Organizations are sometimes limited by the client-server relationship. Thru provides a managed file transfer solution that can act as a client or a server to help you meet requirements such as
- Technology requirements: If you and your partners only use servers to transfer files, Thru can act as a client to make the connection possible.
- Security requirements: If an organization prohibits inbound connections for security or compliance reasons, it can use a client behind its firewall to push files to Thru, which acts as a server.
- Business requirements: If a business has multiple servers and clients to connect, Thru’s web-based interface with flexible workflows can simplify setup and management of endpoints and file routing.
Because client-to-client and server-to-server file transfers are not possible without an entity in between, IT personnel create and manage more endpoints to perform the necessary transfers. By having both client and server functionality, Thru removes endpoint limits and simplifies partner onboarding.
In addition to integrating with clients and servers, Thru integrates with integration platforms, productivity apps and more. Learn more about our file transfer integrations »
