FTP is the acronym of File Transfer Protocol and is the mechanism used to transfer files between computers connected to the Internet (or other IP networks). FTP is one of the original technologies of the Internet and is therefore very well established and supported. Not only can you move files around, but you can also manipulate files, delete files, rename files, set permissions, etc. However, transferring files is probably the main use.

What is an FTP client?

An FTP Client is software that is designed to transfer files back-and-forth between two computers over the Internet. It needs to be installed on your computer and can only be used with a live connection to the Internet.

When you want to transfer web pages from your home/office to your website you will need an FTP client. Some web editors, such as Frontpage, come with an FTP client as standard. Your hosting provider must supply you with an FTP account that is associated with your web directory. You enter these details (server/username/password) into your FTP client and it can then connect to your account allowing you to upload your files. Note, that the FTP client will need to log into the Internet to transfer files to your hosting account.

There are several FTP clients available on the market, for all operating systems. Most of them are shareware, but you can find good FTP clients coming with a freeware license. You may want to test more than one, to find the best program for your need. I'm doing fine with WS FTP.

FTP server response codes

Every time your clients send an FTP command to the server, it replies with a standard 3 digit response code (and a short text message, understandable to humans, too). Below you'll find a list of the FTP return codes with an explanation of what each means.

1XX series: the requested action is being initiated, expect another reply before proceeding with a new command

110 Restart marker reply
120 Service ready in xxx minutes
125 Data connection already open; transfer starting
150 File status okay; about to open data connection

2XX series: the requested action has been successfully completed

200 Command okay
202 Command not implemented, superfluous at this site
211 System status, or system help reply
212 Directory status
213 File status
214 Help message, how to use the server or the meaning of a particular non-standard command
215 NAME system type. Where NAME is an official system name from the list in the Assigned Numbers document
220 Service ready for new user
221 Service closing control connection
225 Data connection open; no transfer in progress
226 Closing data connection. Requested file action successful (example: file transfer or file abort)
227 Entering Passive Mode (h1,h2,h3,h4,p1,p2)
230 User logged in, proceed. Logged out if appropriate
250 Requested file action okay, completed
257 "PATHNAME" created

3XX series: the command has been accepted, but the requested action is dormant, pending receipt of further information

331 User name okay, need password
332 Need account for login
350 Requested file action pending further information

4XX series: the command was not accepted and the requested action did not take place, but the error condition is temporary

421 Service not available, closing control connection.
425 Can't open data connection
426 Connection closed; transfer aborted
450 Requested file action not taken
451 Requested action aborted. Local error in processing
452 Requested action not taken. Insufficient storage space in system

5XX series: the command was not accepted and the requested action did not take place

500 Syntax error, command unrecognized. This may include errors such as command line too long
501 Syntax error in parameters or arguments
502 Command not implemented
503 Bad sequence of commands
504 Command not implemented for that parameter
530 Not logged in. 532 Need account for storing files
550 Requested action not taken. File unavailable (example: file not found, no access)
551 Requested action aborted. Page type unknown
552 Requested file action aborted. Exceeded storage allocation (for current directory or dataset)
553 Requested action not taken. File name not allowed

What is Telnet?

Telnet was one of the first tools built by the architects of the Internet so that resources could be shared easily. Telnet is the means to connect directly to your web site on the server. What this means is that you, from your computer at home or work, can log-on to your hosting space and utilize the software programs or data files located there. An easy way to visualize this is to think of your keyboard directly attached to a distant computer and not to your local computer.

Similar in appearance to the Microsoft DOS prompt, you can type in commands to perform specific functions. The most commonly used commands are simple and easy to remember. There are several functions that you may wish to perform in telnet, such as unzipping files, moving entire directories from one location to another, deleting files or entire directories, setting permissions, etc.

What is SSH ?

If you want to do more than transfer files to your web hosting account, for instance create, edit and test scripts on your host, then you will require command line access, often referred to as shell access. SSH stands for secure shell and allows you to gain shell access to your web hosting account over a secure link. It also helps prevent hackers attempting to gain unauthorized shell access.

Because of the relative power shell access gives to users not all hosting providers will allow their users to have it. Shell access is more use to developers and maintenance engineers than to people who just want to upload new content to their webite, for which FTP can be adequate. When choosing an host, ensure that you will have unlimited FTP access to your account; an SSH account may be very useful, but not essential.

If you're looking for a good SSH client for windows, I would recommend you to try Putty, very good piece of software and freeware.