FTP client for Android

FTP4jAnd is an FTP client library for Android, based on the ftp4j Java library. Control of ftp4j is implemented as an application service, with a helper class provided for service access. Two separate interfaces are also provided for service and download status callbacks.

FTP4jAnd is used in AndPlug music player application for Android devices.

• Prerequisites
• Installation
• Testing
• Usage
• Example
• Credits
• Release History
• License

• Android 4.0.3 (API Level: 15) or later (ICE_CREAM_SANDWICH_MR1)
• Android Gradle Plugin 8.11.1 or later (gradle:8.11.1)
• ftp4j Version 1.7.2

1. Check out a local copy of FTP4jAnd repository
2. Download ftp4j and extract JAR package
3. Build library with Gradle, using Android Studio or directly from the command line

Setup steps:

$ git clone https://github.com/omicronapps/FTP4jAnd.git
$ cd FTP4jAnd/ftplib/libs/
$ unzip -j ftp4j-1.7.2.zip ftp4j-1.7.2/ftp4j-1.7.2.jar

FTP4jAnd includes both instrumented unit tests and a simple test application.

Located under ftplib/src/androidTest.

These tests are run on a hardware device or emulator, and verifies correct operation of the FTPService and FTPController implementations and their usage of the ftp4j library.

Located under app/src/main.

FTP4jAnd is controlled through the following class and interfaces:

• FTPController - service management class
• FTPController.IFTPCallback - service callback interface
• FTPController.IFTPDownload - download status callback interface

Implement FTPController.IFTPCallback callback interface to receive command completion callbacks:

import com.omicronapplications.ftplib.FTPController;

class FTPCallback implements FTPController.IFTPCallback {
...
}

Implement FTPController.IFTPDownload callback interface to receive download status updates:

import com.omicronapplications.ftplib.FTPController;

class FTPDownload implements FTPController.IFTPDownload {
...
}

Create callback instances and controller, and start FTP client service:

FTPCallback callback = new FTPCallback();
FTPDownload download = new FTPDownload();
FTPController controller = new FTPController(getApplicationContext());
controller.setCallbacks(callback, download);
controller.start();

Once service is running, connect to FTP server:

class FTPCallback implements FTPController.IFTPCallback {
    @Override
    public void start() {
        controller.connect("ftp.server.name", 21);
    }
}

Log in user after a connection has been established:

class FTPCallback implements FTPController.IFTPCallback {
    @Override
    public void connect(int exception, String[] message) {
        controller.login("anonymous", "");
    }
}

After the used has been logged in, change the remote directory:

class FTPCallback implements FTPController.IFTPCallback {
    @Override
    public void login(int exception) {
        controller.changeDirectory("...");
    }
}

On entering new remote directory, request list of files:

class FTPCallback implements FTPController.IFTPCallback {
    @Override
    public void changeDirectory(int exception) {
        controller.list();
    }
}

List files in current directory:

class FTPCallback implements FTPController.IFTPCallback {
    @Override
    public void list(int exception, FTPFile[] files) {
        for (FTPFile file : files) {
            // List files
        }
    }
}

Download file from FTP server to local storage:

String remoteFileName = "...";
String localFileName = "...";
controller.download(remoteFileName, localFileName);

Wait for download to complete:

class FTPDownload implements FTPController.IFTPDownload {
    @Override
    public void completed() {
    }
}

Disconnect from FTP server:

controller.disconnect();

After disconnecting from FTP server, stop FTP client service:

class FTPCallback implements FTPController.IFTPCallback {
    @Override
    public void disconnect(int exception) {
        controller.stop();
    }
}

Copyright (C) 2019-2025 Fredrik Claesson

• 1.0.0 Initial release
• 1.1.0 Migrated to AndroidX
• 1.2.0 FTP service refactored, support for multiple download requests
• 1.3.0 Minor bugfix
• 1.4.0 Change to Apache License Version 2.0
• 1.5.0 Target Android 15 (API level 35)

FTP4jAnd is licensed under Apache License Version 2.0.