因项目需求，手机需与设备进行socket连接，连接前需判断手机网络和设备网络是否处于同个子网内。网络搜索无果后，自己根据逻辑写了个粗糙的判断方法，希望能帮助到有需要的人。首篇文章，如有错误，欢迎指正。Thanks♪(･ω･)ﾉ

获取手机当前IP地址

#pragma mark - 获取IP地址

+(NSString *)getIPAddress {
    NSString *address = @"error";
    struct ifaddrs *interfaces = NULL;
    struct ifaddrs *temp_addr = NULL;
    int success = 0;
    // 检索当前接口,在成功时,返回0
    success = getifaddrs(&interfaces);
    if (success == 0) {
        // 循环链表的接口
        temp_addr = interfaces;
        while(temp_addr != NULL) {
            if(temp_addr->ifa_addr->sa_family == AF_INET) {
                // 检查接口是否en0 wifi连接在iPhone上
                if([[NSString stringWithUTF8String:temp_addr->ifa_name] isEqualToString:@"en0"]) {
                    // 得到NSString从C字符串
                    address = [NSString stringWithUTF8String:inet_ntoa(((struct sockaddr_in *)temp_addr->ifa_addr)->sin_addr)];
                }
            }
            temp_addr = temp_addr->ifa_next;
        }
    }
    // 释放内存
    freeifaddrs(interfaces);
    return address;
}

获取子网掩码

#pragma mark - 获取子网掩码

+ (NSString*)getCurrentWifiMessage {
    NSString *address = nil;
    NSString *subNetMask = nil;
    struct ifaddrs *interfaces = NULL;
    struct ifaddrs *temp_addr = NULL;
    int success = 0;
    // retrieve the current interfaces - returns 0 on success
    success = getifaddrs(&interfaces);
    if (success == 0) {
        // Loop through linked list of interfaces
        temp_addr = interfaces;
        while(temp_addr != NULL) {
            if(temp_addr->ifa_addr->sa_family == AF_INET) {
                // Check if interface is en0 which is the wifi connection on the iPhone
                if([[NSString stringWithUTF8String:temp_addr->ifa_name] isEqualToString:@"en0"]) {
                    address = [NSString stringWithUTF8String:inet_ntoa(((struct sockaddr_in *)temp_addr->ifa_netmask)->sin_addr)];
                    subNetMask = [NSString stringWithUTF8String:inet_ntoa(((struct sockaddr_in *)temp_addr->ifa_netmask)->sin_addr)];
                }
            }
            temp_addr = temp_addr->ifa_next;
        }
    }
    // Free memory
    freeifaddrs(interfaces);
    return subNetMask;
}

十进制转二进制

#pragma mark - 十进制转二进制

+ (NSString *)getBinaryByHex:(NSInteger)decimal {
    NSString *binary = @"";
    while (decimal) {
        binary = [[NSString stringWithFormat:@"%ld", decimal % 2] stringByAppendingString:binary];
        if (decimal / 2 < 1) {
            break;
        }
        decimal = decimal / 2 ;
    }
    if (binary.length % 4 != 0) {
        NSMutableString *mStr = [[NSMutableString alloc]init];;
        for (int i = 0; i < 4 - binary.length % 4; i++) {
            [mStr appendString:@"0"];
        }
        binary = [mStr stringByAppendingString:binary];
    }
    return binary;
}

获取某个字符在字符串中的所有位置数组

#pragma mark - 获取某个字符在字符串中的所有位置数组

+ (NSMutableArray *)getRangeStr:(NSString *)text findText:(NSString *)findText {
    NSMutableArray *arrayRanges = [NSMutableArray arrayWithCapacity:3];
    if (findText == nil && [findText isEqualToString:@""]) {
        return nil;
    }
    NSRange rang = [text rangeOfString:findText]; //获取第一次出现的range
    if (rang.location != NSNotFound && rang.length != 0) {
        [arrayRanges addObject:[NSNumber numberWithInteger:rang.location]];//将第一次的加入到数组中
        NSRange rang1 = {0,0};
        NSInteger location = 0;
        NSInteger length = 0;
        for (int i = 0;; i++) {
            if (0 == i)  {
                //去掉这个abc字符串
                location = rang.location + rang.length;
                length = text.length - rang.location - rang.length;
                rang1 = NSMakeRange(location, length);
            } else {
                location = rang1.location + rang1.length;
                length = text.length - rang1.location - rang1.length;
                rang1 = NSMakeRange(location, length);
            }
            //在一个range范围内查找另一个字符串的range
            rang1 = [text rangeOfString:findText options:NSCaseInsensitiveSearch range:rang1];
            if (rang1.location == NSNotFound && rang1.length == 0) {
                break;
            } else//添加符合条件的location进数组
                [arrayRanges addObject:[NSNumber numberWithInteger:rang1.location]];
        }
        return arrayRanges;
    }
    return nil;
}

获取IP或者子网掩码每段的二进制字符串

#pragma mark - 获取IP和子网掩码每段的二进制

+ (NSArray *)fetchBinaryListWithStr:(NSString *)string {
    NSArray *maskPositionList = [self getRangeStr:string findText:@"."];
    NSMutableArray *maskList = [[NSMutableArray alloc] init];
    for (int i = 0; i < [maskPositionList count]; i++) {
        NSString *str;
        if (i == 0) {
            str = [self getBinaryByHex:[[string substringWithRange:NSMakeRange(0, [[maskPositionList objectAtIndex:i] integerValue])] integerValue]];
        } else {
            str = [self getBinaryByHex:[[string substringWithRange:NSMakeRange([[maskPositionList objectAtIndex:i-1] integerValue] + 1, [[maskPositionList objectAtIndex:i] integerValue] - [[maskPositionList objectAtIndex:i-1] integerValue] - 1)] integerValue]];
        }
        for (int i = (int)str.length; i < 12; i++) {
            str = [NSString stringWithFormat:@"0%@",str];
        }
        [maskList addObject:str];
    }
    NSString *lastStr = [self getBinaryByHex:[[string substringWithRange:NSMakeRange([[maskPositionList objectAtIndex:[maskPositionList count] - 1] integerValue] + 1, string.length - [[maskPositionList objectAtIndex:[maskPositionList count] - 1] integerValue] - 1)] integerValue]];
    for (int i = (int)lastStr.length; i < 12; i++) {
        lastStr = [NSString stringWithFormat:@"0%@",lastStr];
    }
    [maskList addObject:lastStr];
    return maskList;
}

二进制的&运算

#pragma mark - 二进制与运算

+ (NSString *)andOperationWithFirst:(NSString *)first andSecond:(NSString *)second {
    NSString *resultStr = nil;
    for (int i = 0; i < first.length; i++) {
        if (i == 0) {
            if ([[first substringWithRange:NSMakeRange(0, 1)] integerValue] == 1 && [[second substringWithRange:NSMakeRange(0, 1)] integerValue] == 1) {
                resultStr = [NSString stringWithFormat:@"1"];
            } else {
                resultStr = [NSString stringWithFormat:@"0"];
            }
        } else {
            if ([[first substringWithRange:NSMakeRange(i, 1)] integerValue] == 1 && [[second substringWithRange:NSMakeRange(i, 1)] integerValue] == 1) {
                resultStr = [NSString stringWithFormat:@"%@1",resultStr];
            } else {
                resultStr = [NSString stringWithFormat:@"%@0",resultStr];
            }
        }
    }
    return resultStr;
}

二进制转十进制

+ (NSString *)getDecimalByBinary:(NSString *)binary {
    NSInteger decimal = 0;
    for (int i = 0; i < binary.length; i++) {
        NSString *number = [binary substringWithRange:NSMakeRange(binary.length - i - 1, 1)];
        if ([number isEqualToString:@"1"]) {
            decimal += pow(2, i);
        }
    }
    return [NSString stringWithFormat:@"%ld",(long)decimal];
}

判断IP是否在同个子网内

+ (BOOL)whetherTheSameSubNetWithDeviceIpStr:(NSString *)deviceIp {
    BOOL result = NO;
    //子网掩码
    NSString *mask = [UtilsMacro getCurrentWifiMessage];
    NSArray *maskList = [UtilsMacro fetchBinaryListWithStr:mask];
    //手机IP地址
    NSString *currentIP = [UtilsMacro getIPAddress];
    NSArray *ipList = [UtilsMacro fetchBinaryListWithStr:currentIP];
    
    NSArray *deviceList = [UtilsMacro fetchBinaryListWithStr:deviceIp];
    
    NSMutableArray *deviceAndResult = [[NSMutableArray alloc] init];
    NSMutableArray *phoneAndResult = [[NSMutableArray alloc] init];
    for (int i = 0; i < [maskList count]; i++) {
        [deviceAndResult addObject:[UtilsMacro getDecimalByBinary:[UtilsMacro andOperationWithFirst:[maskList objectAtIndex:i] andSecond:[deviceList objectAtIndex:i]]]];
        [phoneAndResult addObject:[UtilsMacro getDecimalByBinary:[UtilsMacro andOperationWithFirst:[maskList objectAtIndex:i] andSecond:[ipList objectAtIndex:i]]]];
    }
    
    NSString *deviceResult = [deviceAndResult componentsJoinedByString:@"."];
    NSLog(@"deviceResult:%@",deviceResult);
    NSString *phoneResult = [phoneAndResult componentsJoinedByString:@"."];
    NSLog(@"phoneResult:%@",phoneResult);
    if ([deviceResult isEqualToString:phoneResult]) {
        result = YES;
    } else {
        result = NO;
    }
    return result;
}