What Is An FTP Server? Everything You Need To Know About FTP

Although we can attach images and documents in emails, it has a serious limitation in terms of the size of the attachment you can upload (maybe a few megabytes). If you have a media company that creates high-res photographs and video, then how to send these files that are several gigabytes in size? One of the simplest ways to transfer these large files to clients and remote team members across the globe is through an FTP Server, which acts as a centralized storage point.

The media team can then upload the video files directly to the FTP server. Once the files are uploaded, clients or collaborators can log in using an FTP client and download the files at their convenience. The immediate question you might have is “What is FTP?” or “What is an FTP Server?”.

In this beginner’s guide, we will look at everything related to FTP, which is short for File Transfer Protocol, such as FTP Server, FTP Client, different types of FTP protocols, and several other important components.

What Is FTP?

File Transfer Protocol or FTP is one of the oldest methods for transferring files across networks. It is a network protocol designed specifically for the efficient transfer of data from one host to another using a TCP-based network, such as the Internet. Using FTP, users can upload, download, and manage files on remote servers with ease.

FTP has played a significant role in file-sharing, data exchange, and web hosting for decades. In the early days of the Internet, FTP served as the primary method for uploading web content and distributing software updates. Even though alternatives like SFTP (Secure File Transfer Protocol) and cloud services have gained popularity, FTP is still very popular.

Many web developers rely on FTP to manage and update website files because of its simplicity and support across various platforms. Similarly, businesses that require regular bulk data transfers between remote servers often turn to FTP for its speed and efficiency.

How FTP Works?

The File Transfer Protocol (FTP) follows a client-server model. In this model, two main components interact—an FTP client and an FTP server. The FTP client initiates requests for file transfers, while the FTP server processes those requests.

FTP client can be any software or application specifically designed to connect to an FTP server and transfer files. These clients come in various forms, including command-line utilities and graphical user interfaces (GUIs).

The FTP server, on the other hand, acts as the repository for the files. It manages all incoming requests from clients. The server allows users to upload or download files, depending on the permissions assigned to their account. FTP servers typically run on systems that store large amounts of data, such as cloud servers or enterprise-grade systems.

For every transaction, the FTP server opens two communication channels: a control connection and a data connection. The control connection manages the commands, while the data connection handles the actual file transfer.

When an FTP client wants to upload or download a file, the process begins with the control channel such as login requests, file operations, and directory changes.

Once the server receives a file transfer request, it opens a separate data channel. This channel remains dedicated solely to transferring the file itself. When the client uploads a file, the data moves through this data channel from the client to the server.

Similarly, when downloading a file, the server sends the requested data back to the client using the same channel. This separation between control and data channels allows FTP to perform multiple tasks simultaneously. For example, while transferring files, the client can still send other commands through the control channel without disrupting the data transfer.

Components Of FTP

As mentioned before, the two main components of FTP are: Client and Server.

What Is An FTP Client?

An FTP client is the software or terminal that enables users to connect to an FTP server. Using an FTP client, users can upload, download, and manage files between a local computer and a remote server. The FTP client provides an interface through which the user can communicate with the server. This communication takes place using the FTP protocol, which defines how data should move between devices.

There are several FTP clients available today, each with different features and functionalities. FileZilla is one of the most popular options. It is both open-source and cross-platform and supports FTP, FTPS, and SFTP.

Cyberduck is another widely-used client with support for cloud storage options like Amazon S3 and Microsoft Azure alongside FTP.

FTP clients usually provide two panels in their interface. One panel displays files and directories on the local machine, and the other shows the content of the FTP server. Users can easily manage their files by dragging and dropping them between the panels. In addition to manual file transfers, many FTP clients also support scheduled transfers.

Beyond the graphical interfaces, command-line FTP clients also exist for advanced users who prefer more control over their file transfers. The command-line clients allow users to enter specific FTP commands directly, such as get (retrieve files), put (upload files), ls (list directory contents), and cd (change directories). System administrators and developers, who manage servers frequently, can use command-line clients in automated scripts.

What Is An FTP Server?

An FTP server acts as the host for files that users can access using an FTP client. It provides storage and retrieval capabilities by managing user connections and facilitating file transfers between the server and the client.

Essentially, an FTP server is a centralized location where files are stored and organized, and authorized users or groups can access it over the internet.

FTP servers handle file management part of the connection so that users can upload, download, rename, move, and delete files with ease. FTP servers organize files and directories in a hierarchical structure, similar to file systems used by most operating systems.

FTP servers usually run specialized software that listens for incoming connection requests from FTP clients. Upon receiving a request, the server authenticates the user based on credentials like a username and password.

After successful authentication, the server allows users to browse directories and transfer files according to their permissions. FTP Servers execute commands they receive from FTP Clients.

FileZilla Server (different from FileZilla Client) is one of the most commonly used FTP server applications. Another popular option, vsftpd (Very Secure FTP Daemon), is available only for Linux systems.

Administrators can configure FTP servers to manage not only access but also bandwidth limits, connection timeouts, and the maximum number of simultaneous connections. Logging is a vital function of FTP servers. The server records all activities, such as login attempts, file transfers, and errors.

Types Of FTP Servers

• Anonymous FTP Servers: As the name suggests, users can access anonymous FTP servers without needing to enter a username or password. This feature is common on public FTP servers that host open-access content (open-source software).
• Private FTP Servers: These FTP servers require users to authenticate themselves (by entering a username and password) before gaining access. Some servers adopt two-factor authentication for an added layer of security.
• Managed FTP Servers: Managed FTP servers involve third-party vendors overseeing the server’s operation and maintenance. Organizations often choose this option to decrease the burden of server management.

Types Of FTP Connections: Active And Passive

When using FTP to transfer files, the way the client and server establish communication is very important. FTP operates on two types of connections: Active FTP and Passive FTP.

Active FTP

In Active FTP, the client initiates the control connection with the server. This control connection allows the client to send commands and receive responses. When a file transfer begins, the client does something specific: it opens a dynamic port on its system. Then, it tells the server about this port number. In response, the server connects back to the client through this dynamic port to start the data transfer.

The active mode works well in less restricted network setups. However, active FTP has challenges when dealing with modern security measures, especially firewalls. Since firewalls typically block incoming connections from external sources, the server’s attempt to connect back to the client may get blocked. This behavior leads to failed file transfers in many instances where firewalls or Network Address Translation (NAT) systems protect the client.

Passive FTP

To address the issues with firewall and NAT from an Active FTP, Passive FTP is now more common. In this mode, the client initiates both the control connection and the data connection. After establishing the control connection, the client requests the server to provide a port for the data transfer. The server responds by opening a port on its side and then informs the client about the port number.

With this setup, the client initiates the connection to the server’s specified port. Firewalls generally find this behavior safer because both the control and data connections originate from the client. Since the server does not try to connect back to the client, firewalls are less likely to block the communication.

Types Of File Transfer Protocols

When it comes to file transfer protocols, you often encounter FTP, FTPS, SFTP, SCP, and TFTP when transferring files across networks. While these protocols may seem similar on the surface, they differ in terms of security, ease of use, and efficiency.

FTP (File Transfer Protocol)

FTP is the basic and original File Transfer Protocol. It enables the transfer of files between systems (client and server) over a network. However, FTP has one significant flaw: it sends data, including login credentials, in plain text.

This lack of encryption makes FTP vulnerable to eavesdropping and man-in-the-middle attacks. Despite this flaw, many legacy systems still use FTP, particularly for internal file transfers. FTP typically uses two channels: port 21 for control commands and port 20 for transferring data.

FTPS (FTP Secure)

FTPS extends the functionality of FTP by adding an encryption layer through SSL/TLS for the data and solves the security problems of FTP. This protocol uses two modes: implicit and explicit. In implicit mode, FTPS immediately encrypts all communications, whereas explicit mode negotiates encryption after the initial connection.

SFTP (SSH File Transfer Protocol)

SFTP stands for SSH File Transfer Protocol. It secures file transfer by using a single channel, encrypted by SSH (Secure Shell). Unlike FTP and FTPS, SFTP eliminates the need for multiple channels, making it easier to work with firewalls.

This protocol also brings the ability to resume interrupted transfers, handle file permissions, and manipulate directories efficiently.

SCP (Secure Copy Protocol)

SCP is a straightforward, fast method for transferring files securely between two systems. It runs over SSH, similar to SFTP, and encrypts both authentication and data transfer. However, SCP lacks the advanced file management features of SFTP, focusing solely on copying files.

This protocol doesn’t allow users to perform directory navigation or file manipulation remotely. Due to its minimal overhead and encryption, SCP works well when users need to transfer data quickly between trusted systems.

TFTP (Trivial File Transfer Protocol)

TFTP, short for Trivial File Transfer Protocol, is a lightweight option for transferring files with minimal overhead. It is often used in environments like bootstrapping devices or updating firmware, where simplicity and speed matter more than security. TFTP operates over UDP rather than TCP, which makes it faster but less reliable.

Since TFTP doesn’t include encryption or authentication, users should only use it in trusted, closed-network environments. This protocol works well in scenarios where low file size and minimal transfer complexity dominate. However, in open networks, its lack of security makes it a poor choice.

Comparison Of FTP-Related Protocols

Conclusion

File Transfer Protocol or FTP has played a significant part in digital file transfers since the early 1970s. It is a simple method for moving files between computers regardless of their operating systems.

FTP has remained useful due to its ability to transfer large amounts of data quickly and its compatibility with both command-line and graphical user interfaces. It is very easy to integrate FTP into various workflows (web hosting, content management, and software development).

Even though FTP lacks encryption, which exposes data to risks during transmission, it remains active in certain use cases. Modern protocols like SFTP and FTPS address the security issues of FTP.