Monday, July 30, 2001

Houston, we have a (file transfer) problem

Monday, July 30, 2001

Common wisdom and research conducted by the Bureau of Made-up Statistics suggests that the best way to introduce a web tutorial is to impart a well-meaning, but overly patronizing metaphor. Let's give it a whirl then shall we. How's this? The internet can be thought of as a giant, digital take-away. It's brimming with tasty dishes for you to consume, but sampling them isn't quite as straightforward as dialing a phone number and getting the delivery man to bring them to your door. As already noted in my 'essential applications' tutorial, the most efficient way to get your 'orders' from A to B is to employ a download manager. But which one to choose? If you're a PC user I'd recommend Flashget, while Mac people would be well-advised to use Speed Download.

With either of these applications installed, whenever you click on a file, the browser integration gizmo will kick into action and a download window will appear stating the file size, file location and estimated transfer rate of your chosen download. If everything goes according to plan you should simply be able to click on the 'download now' button and your download manager will take care of the rest. This process can be repeated for a well-nigh infinite number of transfers - you do not have to wait for one file to finish downloading before clicking on the next one you wish to transfer. Each new file will be added to your download queue and transferred sequentially in the order they were clicked - unless of course you choose to rearrange them in order of priority. Once your download manager commences transferring a series of files you can close the web page where you found them and take your metaphorical surf board elsewhere. No more internet babysitting, hoorah!

It's all gone Pete Tong

At this stage there are oodles of sniveling error messages you may be confronted with. In determining the reason for the inaccessibility of a particular file some download managers are more informative than others. If yours ambiguously concludes that if a file cannot be downloaded it must simply be 'busy', it's time to switch to a more insightful application. Below you will find a list of some of the most commonly experienced file transfer errors, and possible workarounds for the non-fatal ones...

~ "File not found" - The file has either been deleted from the server, moved or was incorrectly linked from the outset by the webmaster. It could also be that the web space provider has zapped the file because its presence infringes copyright regulations as detailed in their terms and agreements of use tome. If you're confronted with this message it is probably best to look elsewhere for the same file - perhaps by prompting your download manager to search a variety of mirror servers or by manually scouring File Mirrors.

~ "Unable to connect to..." - You are most likely to see this message if the file you are attempting to download is stored on an FTP site. The explanation - FTPs are actually people's hard drives, which you can access only when their owners are connected to the internet. If you cannot get the file first time, just try again later. If this is happening frequently, the IP address may have been a temporary one and no longer refers to the location where the desired file resides (some ISPs will assign you with a new number each time you log on). The moral of this story is to download goodies from these sites as quickly as possible because they often have a short shelf life.

~ "Too many users - try again later" - Exactly what it says on the tin. The number of simultaneous connections permitted by many FTP sites is limited to a pre-determined maximum to keep download speeds to a reasonable level. Whenever this happens you will have to learn to be patient until it's your turn to connect. Do not 'hammer' the site (repeatedly try to access it) as this can annoy the owner who can then ban you from using it. Another handy hint: if you've been banned, you will be abruptly disconnected from the FTP site without explanation whenever you try to log on - if you do not have a static IP address you can circumvent this dilemma by disconnecting from the internet and re-dialing. When you re-connect you will be allocated with a new IP address which will mimic the appearance of a new user the next time you try to access the FTP site. To make sure this doesn't happen again, open your FTP client's options menu and extend the retry intervals to match the level deemed acceptable by the FTP sys op; anything above 20-ish seconds is reasonable. A better idea perhaps would be to schedule your downloads for a time when fewer users are likely to be accessing the FTP site - early in the morning (UK time) for example, when all the net-hogging American's are fast asleep.

~ "Incorrect password/username/access denied" - The owner is fed up with having hundreds of people clogging up his or her FTP site and has changed the password to prevent you from gaining access. This is very common where 'banner FTP sites' are concerned - those requiring you to click on various banners and hunt for keywords, which form the username and password necessary to access the server. Unsurprisingly this is another money making scheme - these sites are more likely to stay active as the owner has more to gain from keeping them up and running.

~ "Insufficient credits" - You are likely to see a message like this if you are accessing a 'ratio site' - one which requires you to upload a certain quantity of bytes before permitting you to download any of the hosted material. To solve this problem you can instruct your FTP client to begin uploading files whenever you are approaching the designated data transfer limit. This can be arranged simply by placing the files you wish to upload at the bottom of the list of currently downloading files. When you run out of credits they will automatically be uploaded. Alternatively have two FTP sessions open at once - use one to upload and the other to download simultaneously (some sites will limit your access to one connection per IP address so this method will work only when multiple connections are permitted).

~ Servers running Windows NT 4.0 and below do not provide support for the resume function. If you are downloading a file from an unresumable server and the connection is reset you will have to start transferring the file again from scratch. It is best to avoid such files like the plague, especially if they are quite large, but if this isn't feasible, download them one at a time and make sure you do not surf the web simultaneously if you have a slow connection. This will allow you to maximize the bandwidth allocated to your currently downloading file whilst minimizing the likelihood of any interference which could result in transfer interruptions.

~ If when you click on a link it appears as a 'cgi' or 'php' file in the transfer window, the file is either being protected by an anti-leech system or is subject to a file tracking setup (usually just for statistical purposes), making it very awkward to transfer using a download manager. The best way around this complication is to temporarily disable your download manager by holding down the shift button whilst you click on the file and wait to be redirected to the actual target file you wish to download (keep in mind that this will deny you the use of the resume function in many cases). Similarly if you attempt to download a file expecting it to occupy 300mb and it appears in your download directory in a matter of seconds, you can safely assume that you've downloaded the code responsible for redirecting you to the download rather the download itself. There are ways of convincing your download manager to cooperate in downloading these files, but again, in most cases it is quicker and simpler to use the method described above. Some sites simply do not like download managers. Call it a personality clash if you like, but don't waste any more time trying to make the two 'talk' to each other.

~ Note that many more of the errors you will come across while attempting to access FTP sites will not be reported in plain English. In contrast to those listed above, the only clue as to the cause of the problem may be presented in the form of a three digit code, which must first be deciphered before you can attempt to remedy the problem. Below you will find a comprehensive list of these error codes along with their explanations. Note that not all of these codes should be a cause for concern. Many of them will appear simply to keep you informed of the commands currently being executed to facilitate the transfer process.

100 - The requested action is being initiated, expect another reply before proceeding with a new command. 110 - Restart marker reply. 120 - Service ready in x minutes. 125 - Data connection already open, transfer starting. 150 - File status okay, about to open data connection. 200 - 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. 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. Logged out if appropriate. 225 - Data connection open; no transfer in progress. 226 - Closing data connection. Requested file action successful. 227 - Entering Passive Mode. 230 - User logged in, proceed. 250 - Requested file action okay, completed. 257 - Pathname created. 300 - The command has been accepted, but the requested action is being held in abeyance, pending receipt of further information. 331 - User name okay, need password. 332 - Need account for login. 350 - Requested file action pending further information. 400 - The command was not accepted and the requested action did not take place, but the error condition is temporary and the action may be requested again. 421 - Service not available, closing control connection. This may be a reply to any command if the service knows it must shut down. 425 - Can't open data connection. 426 - Connection closed; transfer aborted. 450 - Requested file action not taken. File unavailable. 451 - Requested action aborted: local error in processing. 452 - Requested action not taken. Insufficient storage space in system. 500 - Series Codes: 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. 552 - Requested file action aborted. Exceeded storage allocation (for current directory or data set). 553 - Requested action not taken. File name not allowed.

Even double Dutch makes sense with a double Dutch to English translator!


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