iPhone 网络连接检测(Wifi,3G,Edge)，功能有点像Reachability

这个类可以用来检测用户是否连接到internet. 用法非常简单，只有一个方法，返回 YES或NO。

一个简单的例子：

if ([Connection isConnected]) { ... } else { ... }

这个类的头文件：

// // 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

类的实现文件：

// // 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

最后别忘了添加必要的frameworks: SystemConfiguration and libz.1.1.3.dylib

标题中提到的Reachability也具有检测网络的功能。大家可以参考资料：http://www.raddonline.com/blogs/geek-journal/iphone-sdk-testing-network-reachability/

http://developer.apple.com/iphone/library/samplecode/Reachability/index.html