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Contents
  1. 1. 获取当前手机的dns
  2. 2. 通过ping某个host，查看其相应速度，决定选择最快的host进行网络连接

获取当前手机的dns

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#import <netinet/in.h>
#import <netdb.h>
#import <ifaddrs.h>
#import <arpa/inet.h>
#import <net/ethernet.h>
#import <net/if_dl.h>
#include <resolv.h>

#include <dns.h>
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<sys/socket.h>
#include<unistd.h>
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+ (NSString *)getDNSInfos
{
res_state res = (res_state)malloc(sizeof(struct __res_state));
__uint32_t dwDNSIP = 0;
int result = res_ninit(res);
if (result == 0) {
dwDNSIP = res->nsaddr_list[0].sin_addr.s_addr;
}
NSString *dns = [NSString stringWithUTF8String:inet_ntoa(res->nsaddr_list[0].sin_addr)];
free(res);
return dns;
}

如果报如下错:

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Undefined symbols for architecture arm64: "_res_9_ns_initparse", referenced from: ....

在 build-settings中的other linker flags添加-lresolv

通过ping某个host，查看其相应速度，决定选择最快的host进行网络连接

通过ping一个hostName，获取其解析域名服务器dns.

/**
方法: 获取host的当前dns

参数:
hostName,必选
shortName,可选
allDNS,必选;yes,所有dns;no,当前dns
pingDNSBlock,必选
*/

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- (void)pingWithHostName:(NSString *)hostName
shortName:(NSString *)shortName
allDNS:(BOOL)allDNS
pingDNSBlock:(VSPingDNSBlock)pingDNSBlock
{
//1. 没有网络 or hostName没有，停止ping
if ([VSDevice deviceNetworkType] == VSDeviceNetworkTypeNone || [hostName length]<=0) {
if (pingDNSBlock) {
pingDNSBlock(nil);
}
return;
}

//2. 保存数据
self.desript = shortName;
self.allDNS = allDNS;
self.pingDNSBlock = pingDNSBlock;

//3. 开始ping hostName
[self pingWithHostName:hostName];
}
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- (void)pingWithHostName:(NSString *)hostName{

if (hostName && ![hostName isEqualToString:@""])
{
//1. 记录当前开始ping的起始时间
self.requestTime = [[NSDate date] timeIntervalSince1970];

//2. 进行ping
[self pingHost:hostName];
}
}
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- (void)pingHost:(NSString *)hostName {

//将ping的操作放到全局并发队列，异步执行，可能很耗时
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

//保存得到的所有dns
NSArray *dns = nil;

//是否需要得到所有的dns
if (!self.allDNS) {

//获取当前dns
dns = [self getDNS:hostName];

} else{

//获取所有的dns
dns = [self getAllDNS:hostName];
}

//当前ping操作响应的时间
NSTimeInterval responeTime =[[NSDate date] timeIntervalSince1970];

//响应时间 - 起始时间 = ping操作执行时间
NSTimeInterval time = responeTime - self.requestTime;

//组装hostName、dns、短域名、ping操作执行时间
//回传给调用者
VSPingInfo *pingInfo = [[VSPingInfo alloc] init];
pingInfo.hostName = hostName;
pingInfo.dns  = dns;
pingInfo.shortName = self.desript;
pingInfo.time = time;
dispatch_async(dispatch_get_main_queue(), ^{
[self completePingDNSBlock:pingInfo];
});
});

}

获取所有的dns

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- (NSArray *)getAllDNS:(NSString *)hostName
{

NSMutableArray *dns = nil;
Boolean result = '\0';
CFHostRef hostRef;
CFArrayRef addresses = NULL;

@try {

hostRef = CFHostCreateWithName(kCFAllocatorDefault, (__bridge CFStringRef)hostName);
if (hostRef) {
result = CFHostStartInfoResolution(hostRef, kCFHostAddresses, NULL); // pass an error instead of NULL here to find out why it failed
if (result == TRUE) {
addresses = CFHostGetAddressing(hostRef, &result);
}
}

if (result == TRUE) {
dns = [[NSMutableArray alloc] init];
for(int i = 0; i < CFArrayGetCount(addresses); i++){
struct sockaddr_in* remoteAddr;
CFDataRef saData = (CFDataRef)CFArrayGetValueAtIndex(addresses, i);
remoteAddr = (struct sockaddr_in*)CFDataGetBytePtr(saData);

if(remoteAddr != NULL){
NSString *strDNS =[NSString stringWithCString:inet_ntoa(remoteAddr->sin_addr) encoding:NSASCIIStringEncoding];
[dns addObject:strDNS];
}
}
}

}
@catch (NSException *exception) {

dns = nil;
}
@finally {

}

return dns;
}

获取当前dns

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- (NSArray *)getDNS:(NSString *)hostName
{

NSMutableArray *dns = nil;

const char* szname = [hostName UTF8String];
struct hostent* phot ;
phot = gethostbyname(szname);
struct in_addr ip_addr;
if (phot == NULL){
return nil;
}
memcpy(&ip_addr,phot->h_addr_list[0],4);

char ip[20] = {0};
inet_ntop(AF_INET, &ip_addr, ip, sizeof(ip));

NSString *ipAddr = [NSString stringWithUTF8String:ip];

if (ipAddr && ![ipAddr isEqualToString:@""]) {

dns = [[NSMutableArray alloc] init];
[dns addObject:ipAddr];
}

return dns;
}
Contents
  1. 1. 获取当前手机的dns
  2. 2. 通过ping某个host，查看其相应速度，决定选择最快的host进行网络连接