找了好多资料，终于找到可以用的了。
#include <sys/socket.h>
#import <netinet/in.h>
#import <netinet6/in6.h>
#import <arpa/inet.h>
#import <ifaddrs.h>
#include <netdb.h>
#import <SystemConfiguration/SCNetworkReachability.h>
#import "getgateway.h"
#import <arpa/inet.h> - (NSString *) routerIp {
NSString *address = @"error";
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)
/*/
int i=255;
while((i--)>0)
//*/
{
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"])
{
// Get NSString from C String //ifa_addr
//ifa->ifa_dstaddr is the broadcast address, which explains the "255's"
// address = [NSString stringWithUTF8String:inet_ntoa(((struct sockaddr_in *)temp_addr->ifa_dstaddr)->sin_addr)];
address = [NSString stringWithUTF8String:inet_ntoa(((struct sockaddr_in *)temp_addr->ifa_addr)->sin_addr)];
//routerIP----192.168.1.255 广播地址
NSLog(@"broadcast address--%@",[NSString stringWithUTF8String:inet_ntoa(((struct sockaddr_in *)temp_addr->ifa_dstaddr)->sin_addr)]);
//--192.168.1.106 本机地址
NSLog(@"local device ip--%@",[NSString stringWithUTF8String:inet_ntoa(((struct sockaddr_in *)temp_addr->ifa_addr)->sin_addr)]);
//--255.255.255.0 子网掩码地址
NSLog(@"netmask--%@",[NSString stringWithUTF8String:inet_ntoa(((struct sockaddr_in *)temp_addr->ifa_netmask)->sin_addr)]);
//--en0 端口地址
NSLog(@"interface--%@",[NSString stringWithUTF8String:temp_addr->ifa_name]);
}
}
temp_addr = temp_addr->ifa_next;
}
}
// Free memory
freeifaddrs(interfaces);
in_addr_t i =inet_addr([address cStringUsingEncoding:NSUTF8StringEncoding]);
in_addr_t* x =&i;
unsigned charchar *s=getdefaultgateway(x);
NSString *ip=[NSString stringWithFormat:@"%d.%d.%d.%d",s[0],s[1],s[2],s[3]];
NSLog(@"路由器地址-----%@",ip);
return ip;
}