You may not have heard of cURL, but you've probably used software that uses it. Read More ..
It's an open-source programming toolkit that helps you deal with writing client-side code that deals with URLs.
In the words of the project itself, "cURL groks those URLs."
It's popular because it's a URL Swiss Army knife, making it easy to handle popular protocols like HTTP, SMTP, POP3 and many more. It also supports uploads, downloads, authentication, proxies, cookies and SSL/TLS.
It even supports Gopher, if you remember that far back.
One risk with an all-singing, all-dancing library, of course, is that there's more code to go wrong.