FtpGoServer - A Java FTP server

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FtoGoServer graphic

FtpGoServer is a simple, fast and very small (10K) Java FTP server that can be used on your PC, Mac or Linux machine to allow remote FTP access to a selected part of a computer's file system. Features include:

Intuitive graphical user interface
One click startup with no configuring required
Read only or read/write with anonymous access or based on passwords.
Constant metering of total downloads and uploads in Megabytes
Exposure of only a user designated portion of the file system
Platform independent Java code
No restrictions on number of simultaneous users
Perfect for remote access through Internet Explorer, Netscape, Firefox or other browsers
Warning at start up if no password is set for write access.
10K runtime file

The product was primarily designed for access to files from a browser but any FTP client such as FTP-Go can be used to login, download, upload and manipulate file storage.

Links for FtpGoServer :

Download the server (packaged with the client)
FTP-Go client - a free graphical FTP client

Operational notes

Commands supported are USER, PASS, SYST, PWD, PORT, PASV, LIST, STOR, RETR, MKD, CWD, SIZE, CDUP, DELE, RMD, TYPE, RNFR, RNTO and QUIT.
The apparent file system root for clients is set at startup. This is the only setting that is kept on disk and that is remembered between sessions.
The CWD command is not allowed to make the working directory anything that is not below the root or is the root itself.
The CDUP command will stop at the root and cannot go above it.
TYPE commands always get a positive response but have no meaning. All data transfers will occur in binary (TYPE I) format except for output from the LIST command which is in the default Ascii (TYPE A) format.
If no passwords are set then the PASS command has no meaning but still gets a positive response.
The USER command always gets a positive response but has no meaning, security is checked with PASS only.
RMD can only remove empty directories.
Passwords are entered at runtime and are never stored on disk.
The PWD command response is the virtual path name relative to the assigned root in the local file system. The local root itself is designated as "/". Full local pathnames are never returned.

Further discussion of file referencing

As mentioned, only data in or below the local designated root is available through the server. The product converts any file or directory reference to a fully specified (canonical) unique path for the platform and then checks that the root path prefixes it. Furthermore, before any data access takes place, local file system read/write permissions are checked.

File locking

Simultaneous reads should cause no problems however there is no explicit file locking done when a file is being written to. The underlying platform file system will determine how conflicts are resolved. If a file can't be opened for one operation because it is being used for another purpose by another user then an exception will likely be thrown. This exception will be caught by the server code and the connection attempting the open will be closed.

Logging

The only logging of activity that takes place while the server is running is the totals of uploads and downloads (shown in Megabytes). Additionally the Java console, if it's open, will show any error conditions that are occurring and this can aid problem solving.

Timeouts

The server uses the default settings for all Java sockets. The control socket can optionally have a time out set so that after no control channel activity for 20 minutes, a session will be ended by the sever.

Character encodings

Character encoding for reads and writes on the control socket are explicitly set to "US-ASCII".

Garbage collection

A lot of objects, mainly Strings, are created during an FTP session. Garbage collection is requested after a LIST command has been serviced and when an individual login session ends and that thread exits.

Installing Sun's free Java runtime

To run FtpGoServer you will need to install Java 2 which is a free download from Sun. Double click the "FtpGoServer.jar" file to start the software after installing Java or use the command line "java -jar FtpGoServer.jar".

Source code for FtpGoServer

Source code is available for USD550 on an "as is" basis for incorporation into other products and payable by credit card. Purchase is conditional on acceptance of the licensing terms and conditions.