A lightweight, simple FTP server. Pure Java, no libraries.

Although it's named "minimal", it supports a bunch of features:

• 100% Java, no libraries
• Lightweight
• Supports 57 FTP commands
• TLS/SSL support
• Custom File System support
• Custom User Authentication support
• Custom Commands support
• Support to obsolete commands (some FTP clients might still use them)

The required minimum implementation is already done, however, there are still commands that can be implemented.

• RFC 959 - File Transfer Protocol (33/33)
• RFC 697 - CWD Command of FTP (1/1) (Obsolete)
• RFC 737 - FTP Extension: XSEN (0/3) (Obsolete)
• RFC 743 - FTP extension: XRSQ/XRCP (0/4) (Obsolete)
• RFC 775 - Directory oriented FTP commands (5/5) (Obsolete)
• RFC 1123 - Requirements for Internet Hosts
• RFC 1639 - FTP Operation Over Big Address Records (2/2) (Obsolete)
• RFC 2228 - FTP Security Extensions (3/8)
• RFC 2389 - Feature negotiation mechanism for the File Transfer Protocol (2/2)
• RFC 2428 - FTP Extensions for IPv6 and NATs (2/2)
• RFC 2640 - Internationalization of the File Transfer Protocol (0/1)
• RFC 2773 - Encryption using KEA and SKIPJACK (0/1)
• RFC 3659 - Extensions to FTP (4/4)
• RFC 4217 - Securing FTP with TLS
• RFC 5797 - FTP Command and Extension Registry
• RFC 7151 - File Transfer Protocol HOST Command for Virtual Hosts (1/1)
• draft-twine-ftpmd5-00 - The "MD5" and "MMD5" FTP Command Extensions (2/2) (Obsolete)
• draft-somers-ftp-mfxx-04 - The "MFMT", "MFCT", and "MFF" Command Extensions for FTP (1/3)
• draft-bryan-ftpext-hash-02 - File Transfer Protocol HASH Command for Cryptographic Hashes (1/1)
• draft-bryan-ftp-range-08 - File Transfer Protocol RANG Command for Octet Ranges (0/1)

MinimalFTP is published on JCenter and Maven Central

<dependency>
  <groupId>com.guichaguri</groupId>
  <artifactId>minimalftp</artifactId>
  <version>1.0.6</version>
  <type>pom</type>
</dependency>

compile 'com.guichaguri:minimalftp:1.0.6'

<dependency org='com.guichaguri' name='minimalftp' rev='1.0.6'>
  <artifact name='minimalftp' ext='pom' />
</dependency>

Check out more examples here :)

// Uses the current working directory as the root
File root = new File(System.getProperty("user.dir"));

// Creates a native file system
NativeFileSystem fs = new NativeFileSystem(root);

// Creates a noop authenticator, which allows anonymous authentication
NoOpAuthenticator auth = new NoOpAuthenticator(fs);

// Creates the server with the authenticator
FTPServer server = new FTPServer(auth);

// Start listening synchronously
server.listenSync(21);