Networking is a critical component of many applications today. Networking APIs can take many forms, including TCP/IP communications with the sockets library or interprocess communications using Cocoa’s distributed objects system. Mac OS X’s Darwin layer includes all standard Unix networking technologies and APIs, which are fully accessible from any Cocoa application. In addition to being able to access the Unix APIs, the Foundation framework implements several classes that give applications a higher-level interface for working with networking technologies. This chapter summarizes Foundation’s networking classes, shown in Figure 6-1.