所有的错误代码是在对“CFNetwork的错误代码参考” 小提取CFURL和CFURLConnection错误：
kCFURLErrorUnknown = -998,
kCFURLErrorCancelled = -999,
kCFURLErrorBadURL = -1000,
kCFURLErrorTimedOut = -1001,
kCFURLErrorUnsupportedURL = -1002,
kCFURLErrorCannotFindHost = -1003,
kCFURLErrorCannotConnectToHost = -1004,
kCFURLErrorNetworkConnectionLost = -1005,
kCFURLErrorDNSLookupFailed = -1006,
kCFURLErrorHTTPTooManyRedirects = -1007,
kCFURLErrorResourceUnavailable = -1008,
kCFURLErrorNotConnectedToInternet = -1009,
kCFURLErrorRedirectToNonExistentLocation = -1010,
kCFURLErrorBadServerResponse = -1011,
kCFURLErrorUserCancelledAuthentication = -1012,
kCFURLErrorUserAuthenticationRequired = -1013,
kCFURLErrorZeroByteResource = -1014,
kCFURLErrorCannotDecodeRawData = -1015,
kCFURLErrorCannotDecodeContentData = -1016,
kCFURLErrorCannotParseResponse = -1017,
kCFURLErrorInternationalRoamingOff = -1018,
kCFURLErrorCallIsActive = -1019,
kCFURLErrorDataNotAllowed = -1020,
kCFURLErrorRequestBodyStreamExhausted = -1021,
kCFURLErrorFileDoesNotExist = -1100,
kCFURLErrorFileIsDirectory = -1101,
kCFURLErrorNoPermissionsToReadFile = -1102,
kCFURLErrorDataLengthExceedsMaximum = -1103,