YAFTPd - Yet Another File Transfer Protocol daemon

Introduction

YAFTPd is a small FTP server, born from a programming exercise to implement a FTP server in C language for MAC5910 course in IME-USP. This server only implements passive mode data transfers (since this was the only requirement of this exercise). The server implements the following FTP commands:

• USER
• PASS
• PWD
• CWD
• PASV
• LIST
• RETR
• STOR
• SYST
• PORT
• NOOP
• QUIT

Some of them were not required by this exercise but was implemented anyway for the sake of completeness. Of course, this is still a small subset of the whole FTP protocol defined by RFC959 (and subsequent RFCs).

How to run

You need a GNU environment to compile this source code, since it uses various GNU/POSIX extensions like asprintf, readdir, etc. A relatively recent GNU/Linux distribution should do.

To compile, you can use the included Makefile like this:

$ make -f Makefile

To run the resulted file, just call the generated yaftpd binary like this:

$ ./yaftpd 2121

Where 2121 is the port to run the service.

Tested environment

This program was developed using Arch Linux distribution using the CLANG compiler, version 3.4.2. The program was compiled with GCC compiler, version 4.9.1 too, but only a quick test was made and during this test one bug specific to GCC version was found. This bug was fixed but I don't know if other problems may occur with the use of GCC instead of CLANG.

To run the (more tested) CLANG version, you can install clang in your machine and modify the CC variable in Makefile to clang instead of gcc.

I only tested this program in a single computer, using both localhost (127.0.0.1) and LAN (192.168.0.x). While this should work between multiple machines in the same LAN and even over the Internet this is not tested.

Considerations

Instead of using the suggested proftpd program, that isn't available in Arch Linux repositories, I used the bftpd. So the response messages from yaftpd shouldn't be the same of proftpd, but the response codes should be the same or at least similar. Anyway, I tried to be funny sometimes when creating the user response messages, so don't be surprise if you suddenly find a cow appearing in your screen ;) .

Another thing, while it has "daemon" in it's name, this program doesn't really have a daemon mode (at least yet). I only put the "d" there so it follows the traditional nomenclature of FTP servers (ftpd, proftpd, vsftpd, bftpd).

Thanks

• Daniel Macêdo Batista: the teaching professor of this course and for giving an example code of a simple echo server in C;
• Wireshark: this packet sniffer allowed me to easily investigate the FTP protocol;
• GNU: I used ftp and telnet programs from GNU inetutils during my investigation of the FTP protocol and to validate my implementation. The GNU extensions of C library helped a lot in development too;
• CLANG: this awesome compiler helped a lot during the development of this program;
• Bftpd: like I said in Considerations, I used bftpd instead of proftpd to investigate the FTP protocol locally;
• Mozilla FTP: to confirm my findings I played with Mozilla's public FTP server too.