aj-ftp

aj-ftp is a small Java 8+ client for plain FTP file transfers. It provides a concise API for connecting, authenticating, uploading, and downloading files, while retaining access to the lower-level FTP client when an application needs it.

aj-ftp implements FTP only. It does not provide FTPS or SFTP support.

Add the dependency

<dependency>
    <groupId>com.ajaxjs</groupId>
    <artifactId>aj-ftp</artifactId>
    <version>1.5</version>
</dependency>

Quick start

Create SimpleFtpClient with the FTP host and port, authenticate, perform the required operation, then let try-with-resources close the control connection. Port 21 is the usual FTP control port.

import com.ajaxjs.net.ftp.SimpleFtpClient;

try (SimpleFtpClient ftp = new SimpleFtpClient("ftp.example.com", 21)) {
    ftp.setConnectTimeout(10_000);
    ftp.setReadTimeout(60_000);
    ftp.login("username", "password");
    ftp.enableUtf8(); // Only when the server supports UTF-8 paths.

    ftp.upload("C:/exports/report.zip", "/incoming/report.zip");
    ftp.getFile("/releases/client.zip", "C:/downloads/client.zip");
}

The constructor opens the control connection. login completes user authentication; both authentication and transfers report failures as IOException. Do not log credentials or place them directly in source code.

Choose an operation

Task	High-level API	Notes
Upload a local file	`upload(localPath, remotePath)`	Sends the file in binary mode and validates the final server reply.
Download a remote file	`getFile(remotePath, localPath)`	Writes a temporary file before replacing the destination.
Anonymous FTP	`anonymousLogin()`	Use only when the server explicitly permits anonymous access.
Non-ASCII paths	`enableUtf8()`	Call after connecting, before sending non-ASCII credentials or paths.

Continue with uploading files or downloading files.

Connection and transfer notes

Use anonymousLogin() for FTP servers that permit anonymous access.
Call enableUtf8() after login when file names contain non-ASCII characters and the server supports UTF-8.
setConnectTimeout(milliseconds) and setReadTimeout(milliseconds) configure the client connection.
Transfers use binary mode. The built-in ProgressListener writes byte-count progress to the configured SLF4J logger.
A SimpleFtpClient instance is intended for one caller at a time; do not share it between concurrent threads.

Low-level API

SimpleFtpClient extends com.ajaxjs.net.ftp.sun.ftp.FtpClient. Prefer the high-level upload and getFile methods for normal application code. When using a low-level method that returns a data stream, consume or write the stream, close it, and then call completePendingCommand() to check the server's final reply.