I am behind a proxy server which doesnot allow me to download files over 100MB size. But if somehow I can break the file into few threads each of size less than 100MB , I can download the file. Please help me in writing a program to do so. I know a bit of c and java.

try this:
$ wget "http://.../file" -qO - | split -b 90m - MYFILE

if it doesn't work, tell us why. Give us the specific error messages. What works? Is it only http requests that get blocked? ftp? does the stream get closed after transmitting 100m in your way? Does getting ranges from servers that support it work? Who owns the proxy?

Well I tried to download freebsd iso and i issued the command:

wget http://mymirror.asiaosc.org/freebsd/...i386-disc1.iso --proxy-user=[username] --proxy-passwd=[password] -vO - |split -b 90m - bsd

But it showed the following error message:

--09:41:04-- http://mymirror.asiaosc.org/freebsd/...i386-disc1.iso
=> `-'
Connecting to 202.141.80.20:3128... connected.
Proxy request sent, awaiting response... 403 Forbidden
09:41:12 ERROR 403: Forbidden.

Theproxy blocks http and ftp both. However it only checks the size of the file being downloaded at a time not the whole file size, that's where the trick can be played. Please suggest something. Obviously our sysadmin owns the proxy.

Trying to bypass the security measures that your employer/school/ISP/etc has established is against the LQ Rules

My advice would be to contact your sysadmin and ask him/her for an exemption. -- J.W.

Ok thanks I din't know if a bit of hacking and fun were not allowed in the forum. I promise not to post any such topics anymore.