FileZilla Client is a free, open source FTP client for Windows. It supports FTP, SFTP, and FTPS (FTP over SSL/TLS). The client is available under many platforms, binaries for Windows, Linux and Mac OS X are provided.

FileZilla Server is an FTP server supported by the same project. It supports FTP and FTP over SSL/TLS.

FileZilla’s source code and downloads are hosted on SourceForge. SourceForge featured FileZilla as the Project of the Month in November 2003 and was also voted the best networking program in the 2006 SourceForge.net Community Choice Awards.

• 1xx: Positive Preliminary reply. The action requested is being initiated but there will be another reply before it begins.
• 2xx: Positive Completion reply. The action requested has been completed. The client may now issue a new command.
• 3xx: Positive Intermediate reply. The command was successful, but a further command is required before the server can act upon the request.
• 4xx: Transient Negative Completion reply. The command was not successful, but the client is free to try the command again as the failure is only temporary.
• 5xx: Permanent Negative Completion reply. The command was not successful and the client should not attempt to repeat it again.
• x0x: The failure was due to a syntax error.
• x1x: This response is a reply to a request for information.
• x2x: This response is a reply relating to connection information.
• x3x: This response is a reply relating to accounting and authorization.
• x4x: Not used.
• x5x: These responses indicate the status of the Server file system vis-a-vis the requested transfer or other file system action.

FTP is a way of accessing files on another computer. The computer that is connected to is called a server, the computer that connects to the server is called a client. A server listens on the network for connection requests from other computers. The client can make a connection to the FTP server by using FTP client software. Once connected, the client can do things such as uploading files (putting its own files on the server) to the server, downloading files (taking the server’s files and putting them on his own computer) from the server, and renaming or deleting files on the server.

Many computer platforms support FTP. This allows any computer to connected to a TCP/IP based network to manipulate files on another computer on that network regardless of which operating systems are involved (if the computers permit FTP access). There are many existing FTP client and server programs, many of these are available free.

FTP connection is also seen in cellular phones when trying to transfer or receive data from a computer nearby.