Choose networking API for ios application implementation

There are three networking API types available to implement the network communication function for ios apps.

Foundation API: This is the objective C API, it provides a set of high level NS classes to handle the network connection. This should be your first choice as it is the easiest way to send and receive the data between server and request.  The related document is "URL Loading System Programming Guide"

Core Foundation API: This is a set a C APIs from core foundation framework. These APIs include similar functions as Foundation classes, but provide more control over the network behavior, such as overriding the proxy settings. It should be used if the application cannot use objective C, or the application needs to override the proxy settings on device. The related document is "CFNetwork Programming Guide"

Socket API: This is lower level network C APIs, it should only be used if the application implements its own network protocol other than Http(s) or Ftp. It is discouraged to be used in ios app because it does not activate the cellular radio. The related document is "Networking Programming Topics"

Note for network security testing, the behavior is different when testing on ios simulator or real device. If a certificate is installed on ios 7 simuator system by drag and drop a cert on simulator, the cert is available when querying the application keychain. However, on real device, the certificate installed by configuration profile is not visible when application querying its keychain certificate.