IOS 监听网络状态

日常开发中，出现网络突然断开或异常，在等待网络恢复或连通后需要重新加载数据等情况，那么监听网络状态就是必不可少的。在这里涉及到获取网络状态、监听网络以及网络是否正常通讯。

【获取网络类型】引入以下库文件：

#import <CoreTelephony/CTCarrier.h>
#import <CoreTelephony/CTTelephonyNetworkInfo.h>

【获取网络状态、监听网络】引入以下库文件：

#import <arpa/inet.h>
#import <ifaddrs.h>
#import <netdb.h>
#import <sys/socket.h>
#import <netinet/in.h>
#import <SystemConfiguration/SystemConfiguration.h>

Reachability.h

#import <UIKit/UIKit.h>
 
typedef enum : NSInteger {
    NotReachable = 0,
    ReachableViaWiFi,
    ReachableViaWWAN
} NetworkStatus;

extern NSString *kReachabilityChangedNotification;
 
@interface Reachability : NSObject
 
+ (instancetype)reachabilityWithHostName:(NSString *)hostName;

+ (instancetype)reachabilityWithAddress:(const struct sockaddr *)hostAddress;

+ (instancetype)reachabilityForInternetConnection;
 
- (BOOL)startNotifier;
- (void)stopNotifier;
 
- (NetworkStatus)currentReachabilityStatus;
 
- (BOOL)connectionRequired;
 
@end

Reachability.m

#import <Foundation/Foundation.h>

#import <arpa/inet.h>
#import <ifaddrs.h>
#import <netdb.h>
#import <sys/socket.h>
#import <netinet/in.h>
#import <SystemConfiguration/SystemConfiguration.h>

#import <CoreFoundation/CoreFoundation.h>
 
#import "Reachability.h"
 
NSString *kReachabilityChangedNotification = @"kNetworkReachabilityChangedNotification";
 
#define kShouldPrintReachabilityFlags 1
 
static void PrintReachabilityFlags(SCNetworkReachabilityFlags flags, const char* comment)
{
#if kShouldPrintReachabilityFlags
 
    NSLog(@"Reachability Flag Status: %c%c %c%c%c%c%c%c%c %s\n",
          (flags & kSCNetworkReachabilityFlagsIsWWAN)               ? 'W' : '-',
          (flags & kSCNetworkReachabilityFlagsReachable)            ? 'R' : '-',
 
          (flags & kSCNetworkReachabilityFlagsTransientConnection)  ? 't' : '-',
          (flags & kSCNetworkReachabilityFlagsConnectionRequired)   ? 'c' : '-',
          (flags & kSCNetworkReachabilityFlagsConnectionOnTraffic)  ? 'C' : '-',
          (flags & kSCNetworkReachabilityFlagsInterventionRequired) ? 'i' : '-',
          (flags & kSCNetworkReachabilityFlagsConnectionOnDemand)   ? 'D' : '-',
          (flags & kSCNetworkReachabilityFlagsIsLocalAddress)       ? 'l' : '-',
          (flags & kSCNetworkReachabilityFlagsIsDirect)             ? 'd' : '-',
          comment
          );
#endif
}
 
 
static void ReachabilityCallback(SCNetworkReachabilityRef target, SCNetworkReachabilityFlags flags, void* info)
{
#pragma unused (target, flags)
    NSCAssert(info != NULL, @"info was NULL in ReachabilityCallback");
    NSCAssert([(__bridge NSObject*) info isKindOfClass: [Reachability class]], @"info was wrong class in ReachabilityCallback");
 
    Reachability* noteObject = (__bridge Reachability *)info;
    // Post a notification to notify the client that the network reachability changed.
    [[NSNotificationCenter defaultCenter] postNotificationName: kReachabilityChangedNotification object: noteObject];
}
 
@implementation Reachability
{
    SCNetworkReachabilityRef _reachabilityRef;
}
 
+ (instancetype)reachabilityWithHostName:(NSString *)hostName
{
    Reachability* returnValue = NULL;
    SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithName(NULL, [hostName UTF8String]);
    if (reachability != NULL)
    {
        returnValue= [[self alloc] init];
        if (returnValue != NULL)
        {
            returnValue->_reachabilityRef = reachability;
        }
        else {
            CFRelease(reachability);
        }
    }
    return returnValue;
}
 
 
+ (instancetype)reachabilityWithAddress:(const struct sockaddr *)hostAddress
{
    SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithAddress(kCFAllocatorDefault, hostAddress);
 
    Reachability* returnValue = NULL;
 
    if (reachability != NULL)
    {
        returnValue = [[self alloc] init];
        if (returnValue != NULL)
        {
            returnValue->_reachabilityRef = reachability;
        }
        else {
            CFRelease(reachability);
        }
    }
    return returnValue;
}
 
 
+ (instancetype)reachabilityForInternetConnection
{
    struct sockaddr_in zeroAddress;
    bzero(&zeroAddress, sizeof(zeroAddress));
    zeroAddress.sin_len = sizeof(zeroAddress);
    zeroAddress.sin_family = AF_INET;
    
    return [self reachabilityWithAddress: (const struct sockaddr *) &zeroAddress];
}
 
- (BOOL)startNotifier
{
    BOOL returnValue = NO;
    SCNetworkReachabilityContext context = {0, (__bridge void *)(self), NULL, NULL, NULL};
 
    if (SCNetworkReachabilitySetCallback(_reachabilityRef, ReachabilityCallback, &context))
    {
        if (SCNetworkReachabilityScheduleWithRunLoop(_reachabilityRef, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode))
        {
            returnValue = YES;
        }
    }
    
    return returnValue;
}
 
 
- (void)stopNotifier
{
    if (_reachabilityRef != NULL)
    {
        SCNetworkReachabilityUnscheduleFromRunLoop(_reachabilityRef, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);
    }
}
 
 
- (void)dealloc
{
    [self stopNotifier];
    if (_reachabilityRef != NULL)
    {
        CFRelease(_reachabilityRef);
    }
}
 
 
#pragma mark - Network Flag Handling
 
- (NetworkStatus)networkStatusForFlags:(SCNetworkReachabilityFlags)flags
{
    PrintReachabilityFlags(flags, "networkStatusForFlags");
    if ((flags & kSCNetworkReachabilityFlagsReachable) == 0)
    {
        // The target host is not reachable.
        return NotReachable;
    }
 
    NetworkStatus returnValue = NotReachable;
 
    if ((flags & kSCNetworkReachabilityFlagsConnectionRequired) == 0)
    {
        /*
         If the target host is reachable and no connection is required then we'll assume (for now) that you're on Wi-Fi...
         */
        returnValue = ReachableViaWiFi;
    }
 
    if ((((flags & kSCNetworkReachabilityFlagsConnectionOnDemand ) != 0) ||
        (flags & kSCNetworkReachabilityFlagsConnectionOnTraffic) != 0))
    {
        /*
         ... and the connection is on-demand (or on-traffic) if the calling application is using the CFSocketStream or higher APIs...
         */
 
        if ((flags & kSCNetworkReachabilityFlagsInterventionRequired) == 0)
        {
            /*
             ... and no [user] intervention is needed...
             */
            returnValue = ReachableViaWiFi;
        }
    }
 
    if ((flags & kSCNetworkReachabilityFlagsIsWWAN) == kSCNetworkReachabilityFlagsIsWWAN)
    {
        /*
         ... but WWAN connections are OK if the calling application is using the CFNetwork APIs.
         */
        returnValue = ReachableViaWWAN;
    }
    
    return returnValue;
}
 
 
- (BOOL)connectionRequired
{
    NSAssert(_reachabilityRef != NULL, @"connectionRequired called with NULL reachabilityRef");
    SCNetworkReachabilityFlags flags;
 
    if (SCNetworkReachabilityGetFlags(_reachabilityRef, &flags))
    {
        return (flags & kSCNetworkReachabilityFlagsConnectionRequired);
    }
 
    return NO;
}
 
 
- (NetworkStatus)currentReachabilityStatus
{
    NSAssert(_reachabilityRef != NULL, @"currentNetworkStatus called with NULL SCNetworkReachabilityRef");
    NetworkStatus returnValue = NotReachable;
    SCNetworkReachabilityFlags flags;
    
    if (SCNetworkReachabilityGetFlags(_reachabilityRef, &flags))
    {
        returnValue = [self networkStatusForFlags:flags];
    }
    
    return returnValue;
}
 
 
@end

NetUtil.h

#import <UIKit/UIKit.h>
#import "Reachability.h"

/**
 * 网络工具类
 **/
@interface NetUtil : NSObject

/**
 * 获取当前网络状态
 */
+ (NSInteger)getCurrentNetWorkStatus;

/**
 * 获取当前网络类型
 */
+ (NSString *)getNetworkType;

/**
 * 注册监听网络状态
 */
+ (void)registerObserveNetWorkStatus;

/**
 * 取消监听网络状态
 */
+ (void)unregisterObserveNetWorkStatus;

@end

NetUtil.m

#import <Foundation/Foundation.h>
#import "NetUtil.h"
#import <CoreTelephony/CTCarrier.h>
#import <CoreTelephony/CTTelephonyNetworkInfo.h>

@implementation NetUtil

static Reachability *reachability;

+ (NSInteger)getCurrentNetWorkStatus{
    Reachability *reach = [Reachability reachabilityWithHostName:@"www.apple.com"];
    return [reach currentReachabilityStatus];
}

+ (NSString *)getNetworkType{
    NSString *networkType = @"unknown";
    switch ([self getCurrentNetWorkStatus]) {
        case NotReachable:// 没有网络
        {
            networkType = @"no network";
        }
            break;
        case ReachableViaWiFi:// Wifi
        {
            networkType = @"Wifi";
        }
            break;
        case ReachableViaWWAN:// 手机自带网络
        {
            // 获取手机网络类型
            CTTelephonyNetworkInfo *info = [[CTTelephonyNetworkInfo alloc] init];
            NSString *currentStatus = info.currentRadioAccessTechnology;
            if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyGPRS"]) {
                networkType = @"GPRS";
            }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyEdge"]) {
                networkType = @"2.75G EDGE";
            }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyWCDMA"]){
                networkType = @"3G";
            }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyHSDPA"]){
                networkType = @"3.5G HSDPA";
            }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyHSUPA"]){
                networkType = @"3.5G HSUPA";
            }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyCDMA1x"]){
                networkType = @"2G";
            }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyCDMAEVDORev0"]){
                networkType = @"3G";
            }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyCDMAEVDORevA"]){
                networkType = @"3G";
            }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyCDMAEVDORevB"]){
                networkType = @"3G";
            }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyeHRPD"]){
                networkType = @"HRPD";
            }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyLTE"]){
                networkType = @"4G";
            } else {
                networkType = @"WWAN";
            }
        }
            break;
        default:
            break;
    }

    return networkType;
}

+ (void)registerObserveNetWorkStatus{
    // 创建Reachability
    reachability = [Reachability reachabilityForInternetConnection];
    // 开始监控网络（一旦网络状态发生改变，就会发出通知kReachabilityChangedNotification）
    [reachability startNotifier];
}

+ (void)unregisterObserveNetWorkStatus{
    if (reachability) {
        [reachability stopNotifier];
    }
}

@end