FTP (File Transfer Protocol)
One of the easiest ways to send files through the internet is through FTP, which stands for File Transfer Protocol. FTP works using a client-server architecture, which means many clients (remote processors) get information from a server, or host computer. A program called a daemon on the FTP server permits clients to download or upload files. Usually FTP is used just for downloading though. Sometimes usernames and passwords are required to access files. If its your server, you can upload web pages and files to your site.
- Transfers data efficiently and reliably
- Promotes consistency in file storage
- Supports the indirect use of remote computers
- Encourages the sharing of files
The Control/Data Connection:
- The Control Connection is a bilateral link between the server Protocol Interpreter (PI) and the User PI. This is separate from the Data Connection in which actual file data is transferred with.
- The Control Connection contains control commands in which user and server messages and passed through. The connection must be established for the Data Connection pipe to be functional.
- -Uses a telnet protocol
- -Commands are ASCII based
- -Use of the Control Connection is wide spread, meaning most servers will set up a workable environment for it.
The messages sent through the Control Connection are in the form, 3 digits (roughly 8 bits status code), each representing a specific command. A text message is accompanied with the number but is not used by the program but rather for humans to interpret.
The first digit represents the following:
- 1: Positive Preliminary reply (Received message, waiting)
- 2: Positive Completion Reply (Done/Success)
- 3: Positive Intermediate Reply (Waiting for more information)
- 4. Transient Negative Completion (error, retry)
- 5. Permanent Negative Reply (error - abort)
The second digit represents the following:
- 0: Problem with command syntax
- 1: Information request
- 2: Problem with Connection
- 3: Problem with login
- 4: Unknown
- 5: File System error
The third represents a specific error in the a function group