Building Internet Applications with APL+Win: FTPClientX and HTTPClientX William Parke Today's computer applications often need networked file and information transfer. Network services developed with APL+Win® can take advantage of its NI socket facility as well as its ability to operate as an ActiveX server, which greatly enhances management of asynchronous events. This article will describe two Internet utilities, FTPClientX and HTTPClientX, developed as APL+Win ActiveX Server (APLW-XS) applications. Internet, there is an inherent loss of control, by the application/programmer, when using these protocols. In addition, FTP servers do not all respond in exactly the same way, further necessitating a patient and flexible design as well as experimentation and trialand-error during development. The second project was to develop a HyperText Transfer Protocol (HTTP) client to download Web pages. HTTP is a much simpler protocol, and the associated socket events are easier to manage. As it turns out, HTTP also has more interesting uses than FTP, as will be described below. The Designs I had similar goals in mind as I approached both projects: Consistent, object-oriented programmer interface Usage in both a graphical user interface (GUI) and program- or batch-mode environments Programmer-friendly translations of the FTP and HTTP methods The
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