Indika Bandara wrote: > hello, > > sorry if this is a wrong question in the wrong place. since many > knowelegable persons are in this forum thought of askin this > (programmers are supposed to know every thing right?) > > > How do the web clients which download files by parts work?(e.g > prozilla, download accelerator-DAP etc) > > from what i read here is how things work usually > 1. my web client requests for a file at www.abc.com/file.txt > 2. remote http server replies with file size and other headers > 3. my client does the download > > the question arises how my client can request files by part as the > above mentioned clients do
The server has to support requests for parts of any given document (see the HTTP/1.1 RFC specifications). The tools you mention simply check to see if the server supports this feature of HTTP/1.1 and, if so, sends one or more requests for the data. If the connection breaks, the tool simply "resumes" the download by starting where it left off. Nothing really fancy except that most "download accelerators" have spyware included. Also, some download sites use a "queue" sort of setup and specifically prevent "download accelerators" from working (e.g. www.3dgamers.com). If you want to watch the action, use Ethereal to capture the packets being sent back and forth between the server and client. -- Thomas Hruska CubicleSoft President Ph: 517-803-4197 *NEW* VerifyMyPC 2.0 Change tracking and management tool. Reduce tech. support times from 2 hours to 5 minutes. Free for personal use, $10 otherwise. http://www.CubicleSoft.com/VerifyMyPC/
