libcurl
http://curl.haxx.se/libcurl/ libcurl - the multiprotocol file transfer library
libcurl - the multiprotocol file transfer library
libcurl is a free and easy-to-use client-side URL transfer library, supporting DICT, FILE, FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, POP3, POP3S, RTMP, RTSP, SCP, SFTP, SMTP, SMTPS, TELNET and TFTP. libcurl supports SSL certificates, HTTP POST, HTTP PUT, FTP uploading, HTTP form based upload, proxies, cookies, user+password authentication (Basic, Digest, NTLM, Negotiate, Kerberos), file transfer resume, http proxy tunneling and more!
libcurl is highly portable, it builds and works identically on numerous platforms, including Solaris, NetBSD, FreeBSD, OpenBSD, Darwin, HPUX, IRIX, AIX, Tru64, Linux, UnixWare, HURD, Windows, Amiga, OS/2, BeOs, Mac OS X, Ultrix, QNX, OpenVMS, RISC OS, Novell NetWare, DOS and more...
libcurl is free , thread-safe , IPv6 compatible , feature rich , well supported , fast , thoroughly documented and is already used by many known, big and successful companies and numerous applications .
Go to the regular curl download page and get the latest curl package, or one of the specific libcurl packages listed.
You use libcurl with the provided C API or one of the almost 40 available bindings .
Check out our using libcurl page for general hints and advice, the free HTTP client library comparison . or read the comparisons against libwww and WinInet .
libcurl is most probably the most portable, most powerful and most often used C-based multi-platform file transfer library on this planet - be it open source or commercial.