Netscape Helper Applications Netscape helper applications work in much the same way as Netscape plug-ins. When the Navigator encounters an unknown media type, it first consults an internal plug-in list. Finding no plug-ins, it turns to the Helpers configuration. If a helper application is associated with the given media type, it is started by the Navigator. A helper application can be any software program that runs on your system.
Many helpers have nothing to do with networking.
Consider using Microsoft Paint as a bitmap viewer. Navigator encounters a bitmap file, downloads it, and opens Paint with the given filename. Paint operates on the local file normally. A good example of a sockets-based helper application is Progressive Networks' RealAudio Player, which is shown in Figure 4.1. The RealAudio Player plays real-time sound over the Internet.