iPhone网络编程之监视网络连接

转载自http://hi.baidu.com/popln/blog/item/e6ed14884b2fa4a60f2444d1.html

　　在当前的run循环中通过异步查询UIDevice当前的标志和网络状态，对网络连接状态进行监视。当连接状态变化时,观察者(observer)会以回调函数的形式接收到通知，从而做出相应的处理。

#import <SystemConfiguration/SystemConfiguration.h>
#include <netdb.h>
#import <dlfcn.h>
#import "UIDevice-Reachability.h"

@implementation UIDevice (Reachability)
SCNetworkConnectionFlags connectionFlags;
SCNetworkReachabilityRef reachability;

#pragma mark Checking Connections
+ (void) pingReachabilityInternal
{
    if (!reachability)
    {
        BOOL ignoresAdHocWiFi = NO;
        struct sockaddr_in ipAddress;
        bzero(&ipAddress, sizeof(ipAddress));
        ipAddress.sin_len = sizeof(ipAddress);
        ipAddress.sin_family = AF_INET;
        ipAddress.sin_addr.s_addr = htonl(ignoresAdHocWiFi ? INADDR_ANY : IN_LINKLOCALNETNUM);
        
        reachability = SCNetworkReachabilityCreateWithAddress(kCFAllocatorDefault, (struct sockaddr *)&ipAddress);
        CFRetain(reachability);
    }
    
    // Recover reachability flags
    BOOL didRetrieveFlags = SCNetworkReachabilityGetFlags(reachability, &connectionFlags);
    if (!didRetrieveFlags) 
　　　　printf("Error. Could not recover network reachability flags\n");
}

#pragma mark Monitoring reachability
static void ReachabilityCallback(SCNetworkReachabilityRef target, SCNetworkConnectionFlags flags, void* info)
{
    NSAutoreleasePool *pool = [NSAutoreleasePool new];
    [(id)info performSelector:@selector(reachabilityChanged)];
    [pool release];
}

// 开启网络连接监视
+ (BOOL) scheduleReachabilityWatcher: (id) watcher
{
    if (![watcher conformsToProtocol:@protocol(ReachabilityWatcher)])
    {
        NSLog(@"Watcher must conform to ReachabilityWatcher protocol. Cannot continue.");
        return NO;
    }
    
    [self pingReachabilityInternal];
    
    SCNetworkReachabilityContext context = {0, watcher, NULL, NULL, NULL};
    if(SCNetworkReachabilitySetCallback(reachability, ReachabilityCallback, &context))
    {
        if(!SCNetworkReachabilityScheduleWithRunLoop(reachability, CFRunLoopGetCurrent(), kCFRunLoopCommonModes))
        {
            NSLog(@"Error: Could not schedule reachability");
            SCNetworkReachabilitySetCallback(reachability, NULL, NULL);
            return NO;
        }
    }
    else
    {
        NSLog(@"Error: Could not set reachability callback");
        return NO;
    }
    
    return YES;
}

+ (void) unscheduleReachabilityWatcher
{
    SCNetworkReachabilitySetCallback(reachability, NULL, NULL);
    if (SCNetworkReachabilityUnscheduleFromRunLoop(reachability, CFRunLoopGetCurrent(), kCFRunLoopCommonModes))
        NSLog(@"Unscheduled reachability");
    else
        NSLog(@"Error: Could not unschedule reachability");
            
    CFRelease(reachability);
    reachability = nil;
}

@end