在macos上获取套接字对等IP地址的正确方法

我正在尝试这个简单的代码,去获取客户的IP地址。它在FreeBSD上运行良好,但在Mac上奇怪地返回零。感到困惑,不明白怎么了。拜托,救命啊。

#include <stdio.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#include <arpa/inet.h>

int main() {
    int s, c;
    socklen_t len;
    struct sockaddr_in saddr, caddr;

    if ((s = socket(PF_INET, SOCK_STREAM, 0)) == -1) {
        printf("socket()\n"); exit(1);
    }
    
    saddr.sin_family = AF_INET;
    saddr.sin_addr.s_addr = htonl(INADDR_ANY);
    saddr.sin_port = htons(9090);

    if ((bind(s, (struct sockaddr *)&saddr, sizeof(saddr))) != 0) {
        printf("bind()\n"); exit(1);
    }

    if ((listen(s, 5)) != 0) {
        printf("listen()\n"); exit(1);
    }

    if ((c = accept(s, (struct sockaddr *)&caddr, &len)) < 0) {
        printf("accept()\n"); exit(0);
    }

    char ipstr[INET6_ADDRSTRLEN];
    inet_ntop(AF_INET, &caddr.sin_addr, ipstr, len);
    
    printf("Client IP address: [%s:%d]\n", ipstr, ntohs(caddr.sin_port));

    close(c);  close(s);

    return 0;
}

在FreeBSD上:

Client IP address: [127.0.0.1:17225]

在Mac上:

Client IP address: [0.0.0.0:0]