学步园

//  

//  Connection.h     

#import <Foundation/Foundation.h>  

#import <SystemConfiguration/SystemConfiguration.h>  

#import <netinet/in.h>  

#import <arpa/inet.h>  

#import <netdb.h>   

@interface Connection : NSObject {  

} 

+ (BOOL) isConnected;  

@end

//  

//  Connection.m 

//    

#import "Connection.h"  

@implementation Connection  

+ (BOOL) isConnected {  

    // Create zero addy  

    struct sockaddr_in zeroAddress;  

    bzero(&zeroAddress, sizeof(zeroAddress));  

    zeroAddress.sin_len = sizeof(zeroAddress);  

    zeroAddress.sin_family = AF_INET;  

    // Recover reachability flags  

    SCNetworkReachabilityRef defaultRouteReachability = SCNetworkReachabilityCreateWithAddress(NULL, 
   (struct sockaddr *)&zeroAddress);  

    SCNetworkReachabilityFlags flags;  

    BOOL didRetrieveFlags = SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags);  

    CFRelease(defaultRouteReachability);  

    if (!didRetrieveFlags) {  

        NSLog(@"Error. Could not recover network reachability flags");  

        return NO;  

    }  

    BOOL isReachable = flags & kSCNetworkFlagsReachable;  

    BOOL needsConnection = flags & kSCNetworkFlagsConnectionRequired;  

    BOOL nonWiFi = flags & kSCNetworkReachabilityFlagsTransientConnection;  

    NSURL *testURL = [NSURL URLWithString:@"http://www.google.com/"];  

    NSURLRequest *testRequest = [NSURLRequest requestWithURL:testURL  cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:20.0];  

    NSURLConnection *testConnection = [[[NSURLConnection alloc] 
    initWithRequest:testRequest delegate:self] autorelease];  

    return ((isReachable && !needsConnection) || nonWiFi) ? (testConnection ? YES : NO) : NO;  

} 

@end