如何在iOS應用中獲取對等IP地址（iOS-非iOS設備對等）

Question

我正在將我的iOS設備與未啟用iOS Direct-WiFi的設備建立對等關系。 在我的iOS應用程序中，我想啟動與遠程服務器（即非iOS設備的服務器）的連接。 為此，首先我需要將讀寫流綁定到主機IP和端口，如下所示：

NSInputStream *inputStream;
NSOutputStream *outputStream;

CFReadStreamRef rdStream;
CFWriteStreamRef wrStream;
NSString *ipAddr = ???    /* not know at design time */
UInt32 portNum = 4210;    /* specified at design time */

CFStreamCreatePairWithSocketToHost(kCFAllocatorDefault, (__bridge CFStringRef)ipAddr, portNum, &rdStream, &wrStream);

inputStream = (__bridge NSInputStream *)rdStream;
outputStream = (__bridge NSOutputStream *)wrStream;

...然后，對於每個流，我設置委托，在運行循環中安排時間表，然后打開。 現在它們可以使用了。 顯然，在我的iOS設備中，我轉到“設置”內置應用程序，然后選擇要與之對等的服務器的WiFi，這樣我的iOS設備和另一台設備將位於同一網絡上。

我的問題是服務器IP地址在我的應用程序設計時未知，因此我想在我的應用程序運行時以編程方式找出此IP地址。 可能嗎？ 如果是這樣，請給我一個主意。

謝謝

Answer 1

這將為您提供一系列IP。 出於我的目的，第二個元素是主機名的IP：

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

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

...

    const char* hostnameC = [yourHostName UTF8String];

struct addrinfo hints, *res;
struct sockaddr_in *s4;
struct sockaddr_in6 *s6;
int retval;
char buf[64];
NSMutableArray *result; //the array which will be return
NSMutableArray *result4; //the array of IPv4, to order them at the end
NSString *previousIP = nil;

memset (&hints, 0, sizeof (struct addrinfo));
hints.ai_family = PF_UNSPEC;//AF_INET6;
hints.ai_flags = AI_CANONNAME;
//AI_ADDRCONFIG, AI_ALL, AI_CANONNAME,  AI_NUMERICHOST
//AI_NUMERICSERV, AI_PASSIVE, OR AI_V4MAPPED

retval = getaddrinfo(hostnameC, NULL, &hints, &res);
if (retval == 0)
{

    if (res->ai_canonname)
    {
        result = [NSMutableArray arrayWithObject:[NSString stringWithUTF8String:res->ai_canonname]];
    }
    else
    {
        //it means the DNS didn't know this host
        return;
    }
    result4= [NSMutableArray array];
    while (res) {
        switch (res->ai_family){
            case AF_INET6:
                s6 = (struct sockaddr_in6 *)res->ai_addr;
                if(inet_ntop(res->ai_family, (void *)&(s6->sin6_addr), buf, sizeof(buf))
                   == NULL)
                {
                    NSLog(@"inet_ntop failed for v6!\n");
                }
                else
                {
                    //surprisingly every address is in double, let's add this test
                    if (![previousIP isEqualToString:[NSString stringWithUTF8String:buf]]) {
                        [result addObject:[NSString stringWithUTF8String:buf]];
                    }
                }
                break;

            case AF_INET:
                s4 = (struct sockaddr_in *)res->ai_addr;
                if(inet_ntop(res->ai_family, (void *)&(s4->sin_addr), buf, sizeof(buf))
                   == NULL)
                {
                    NSLog(@"inet_ntop failed for v4!\n");
                }
                else
                {
                    //surprisingly every address is in double, let's add this test
                    if (![previousIP isEqualToString:[NSString stringWithUTF8String:buf]]) {
                        [result4 addObject:[NSString stringWithUTF8String:buf]];
                    }
                }
                break;
            default:
                NSLog(@"Neither IPv4 nor IPv6!");

        }
        //surprisingly every address is in double, let's add this test
        previousIP = [NSString stringWithUTF8String:buf];

        res = res->ai_next;
    }
}else{
    NSLog(@"no IP found");
    return;
}

...