I am trying to add SimplePing class to my iphone project.Here is the link of the class:http://developer.apple.com/library/mac/#samplecode/SimplePing/Introduction/Intro.html 

I am getting these 9 errors. I dont have any idea that where they are coming from:

"\_CFHostGetAddressing", referenced from:
 -[SimplePing \_hostResolutionDone] in SimplePing.o
 "\_CFHostScheduleWithRunLoop", referenced from:
 -[SimplePing start] in SimplePing.o
 "\_kCFStreamErrorDomainNetDB", referenced from:
 \_kCFStreamErrorDomainNetDB$non\_lazy\_ptr in SimplePing.o
 (maybe you meant: \_kCFStreamErrorDomainNetDB$non\_lazy\_ptr)
 "\_CFHostCreateWithName", referenced from:
 -[SimplePing start] in SimplePing.o
 "\_CFHostSetClient", referenced from:
 -[SimplePing start] in SimplePing.o
 -[SimplePing \_stopHostResolution] in SimplePing.o
 "\_kCFGetAddrInfoFailureKey", referenced from:
 \_kCFGetAddrInfoFailureKey$non\_lazy\_ptr in SimplePing.o
 (maybe you meant: \_kCFGetAddrInfoFailureKey$non\_lazy\_ptr)
 "\_CFHostUnscheduleFromRunLoop", referenced from:
 -[SimplePing \_stopHostResolution] in SimplePing.o
 "\_kCFErrorDomainCFNetwork", referenced from:
 \_kCFErrorDomainCFNetwork$non\_lazy\_ptr in SimplePing.o
 (maybe you meant: \_kCFErrorDomainCFNetwork$non\_lazy\_ptr)
 "\_CFHostStartInfoResolution", referenced from:
 -[SimplePing start] in SimplePing.o

Please help !!