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從 sockaddr 結構中獲取 IPV4 地址

[英]Getting IPV4 address from a sockaddr structure

如何將 IP 地址提取到字符串中? 我找不到告訴我char sa_data[14]是如何編碼的參考。

只需將整個sockaddr結構轉換為sockaddr_in 然后你可以使用:

char *ip = inet_ntoa(their_addr.sin_addr)

檢索標准 ip 表示。

inet_ntoa()適用於 IPv4; inet_ntop()適用於 IPv4 和 IPv6。

給定一個輸入struct sockaddr *res ,這里有兩個代碼片段(在 macOS 上測試):

使用 inet_ntoa()

#include <arpa/inet.h>

struct sockaddr_in *addr_in = (struct sockaddr_in *)res;
char *s = inet_ntoa(addr_in->sin_addr);
printf("IP address: %s\n", s);

使用 inet_ntop()

#include <arpa/inet.h>
#include <stdlib.h>

// obviously INET6_ADDRSTRLEN is expected to be larger
// than INET_ADDRSTRLEN, but this may be required in case
// if for some unexpected reason IPv6 is not supported, and
// INET6_ADDRSTRLEN is defined as 0
// but this is not very likely and I am aware of no cases of
// this in practice (editor)
char s[INET6_ADDRSTRLEN > INET_ADDRSTRLEN ? INET6_ADDRSTRLEN : INET_ADDRSTRLEN]
    = '\0';

switch(res->sa_family) {
    case AF_INET: {
        struct sockaddr_in *addr_in = (struct sockaddr_in *)res;

        ////char s[INET_ADDRSTRLEN] = '\0';
            // this is large enough to include terminating null

        inet_ntop(AF_INET, &(addr_in->sin_addr), s, INET_ADDRSTRLEN);
        break;
    }
    case AF_INET6: {
        struct sockaddr_in6 *addr_in6 = (struct sockaddr_in6 *)res;
        
        ////char s[INET6_ADDRSTRLEN] = '\0';
            // not sure if large enough to include terminating null?

        inet_ntop(AF_INET6, &(addr_in6->sin6_addr), s, INET6_ADDRSTRLEN);
        break;
    }
    default:
        break;
}
printf("IP address: %s\n", s);

Emil 的回答是正確的,但我的理解是inet_ntoa已被棄用,而您應該使用inet_ntop 如果您使用的是 IPv4,請將您的struct sockaddrsockaddr_in 您的代碼將如下所示:

struct addrinfo *res;   // populated elsewhere in your code
struct sockaddr_in *ipv4 = (struct sockaddr_in *)res->ai_addr;
char ipAddress[INET_ADDRSTRLEN];
inet_ntop(AF_INET, &(ipv4->sin_addr), ipAddress, INET_ADDRSTRLEN);

printf("The IP address is: %s\n", ipAddress);

查看這個很棒的資源以獲得更多解釋,包括如何對 IPv6 地址執行此操作。

一旦sockaddrsockaddr_in ,它就會變成這樣:

struct sockaddr_in {
    u_short     sin_family;
    u_short     sin_port;
    struct      in_addr sin_addr;
    char        sin_zero[8];
};

您可以將getnameinfo 用於 WindowsLinux

假設您有一個很好的(即它的成員具有適當的值) sockaddr*稱為pSockaddr

char clienthost[NI_MAXHOST];  //The clienthost will hold the IP address.
char clientservice[NI_MAXSERV];
int theErrorCode = getnameinfo(pSockaddr, sizeof(*pSockaddr), clienthost, sizeof(clienthost), clientservice, sizeof(clientservice), NI_NUMERICHOST|NI_NUMERICSERV);

if( theErrorCode != 0 )
{
    //There was an error.
    cout << gai_strerror(e1) << endl;
}else{
    //Print the info.
    cout << "The ip address is = " << clienthost << endl;
    cout << "The clientservice = " << clientservice << endl;
}

鍵入鑄造sockaddrsockaddr_in使用和IPv4的檢索inet_ntoa

char * ip = inet_ntoa(((struct sockaddr_in *)sockaddr)->sin_addr);

以下程序解析給定域:

$ gcc a.c

$ ./a.out google.com
AF_INET: 216.58.214.238
AF_INET6: 2a00:1450:400d:803::200e

$ ./a.out google.com af_inet
AF_INET: 216.58.214.238

ac

#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>

int
main(int argc, char *argv[])
{
    struct addrinfo hints, *res, *cres;
    int r;
    char s[INET6_ADDRSTRLEN];

    memset(&hints, 0, sizeof(hints));
    if (argc > 2)
        hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_DGRAM;

    r = getaddrinfo(argv[1], NULL, &hints, &res);
    if (r) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(r));
        exit(EXIT_FAILURE);
    }

    for (cres = res; cres; cres = cres->ai_next) {
        switch (cres->ai_family) {
        case AF_INET:
            inet_ntop(AF_INET, &((struct sockaddr_in *)cres->ai_addr)->sin_addr, s, INET6_ADDRSTRLEN);
            printf("AF_INET: %s\n", s);
            break;
        case AF_INET6:
            inet_ntop(AF_INET6, &((struct sockaddr_in6 *)cres->ai_addr)->sin6_addr, s, INET6_ADDRSTRLEN);
            printf("AF_INET6: %s\n", s);
            break;
        }
    }

    freeaddrinfo(res);
}

另一個例子可以在這里找到。

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