cURL is a free open source tool, which allows you to get and post using HTTP(s), with full support of cookies, Referrer, User-Agent, authentication and much more. Besides, it also allows you to use FTP(s) and other protocols. It allows to automatically fill web forms and handles receiving the data.
It is cross-platform, requires no installation on Windows and is already available on Mac OS X. Last but not least, it can be controlled using 4D 2004's new command LAUNCH EXTERNAL PROCESS. This technical note shows how to use this tool.
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