title: Xcode 8.3.2 cannot find CocoaAsyncSocket.h
body: <p>I'm an old-school c/c++ programmer new to the Xcode IDE, tasked with creating an app for iOS that can receive data from an IPv4 multicast address.  Since Swift 3 doesn't have an API for joining to a multicast address or binding to a port, I need to embed Objective-C code in the Swift code.</p>
  
  <p>I have found a number of ways to do it with an asynch UDP socket, but when I reference either CocoaAsyncSocket.h (or GCDAsyncUdpSocket.h), I get an error "Module 'CocoaAsyncSocket' not found." Indeed, if I do a file search, I come up dry.</p>
  
  <p>I don't see that Objective-C or its libraries can be downloaded from Apple, and they didn't come along when I downloaded Xcode 8.3.2, nor can I locate an Open Source version.  Can anyone provide some pointers?  Thanks!</p>