FtpGoServer

The FtpGoServer application was designed to be a simple, fast and very small 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.

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.

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.

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.

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".

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.