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我正在学习 Beej 的套接字教程。为什么下面的调用socket在 iPhone 模拟器中不起作用？

    int status;
    struct addrinfo hints;
    struct addrinfo *servinfo;
    char ipstr[INET6_ADDRSTRLEN];

    memset(&hints, 0, sizeof(hints));
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;

    if ((status = getaddrinfo("www.yahoo.com", 
                              "80", 
                              &hints, 
                              &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo error: %s\n", gai_strerror(status));
        exit(1);
    }

    for(struct addrinfo *p = servinfo; p != NULL; p = p->ai_next) {
        void *addr;
        char *ipver;

        if (p->ai_family == AF_INET) {
            struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr;
            addr = &(ipv4->sin_addr);
            ipver = "IPv4";
        } else {
            struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ai_addr;
            addr = &(ipv6->sin6_addr);
            ipver = "IPv6";
        }

        inet_ntop(p->ai_family, addr, ipstr, sizeof(ipstr));
        printf("  %s: %s\n", ipver, ipstr);

        int socketfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
        if (socketfd)
            printf("errno: %d\n", errno);
    }

    freeaddrinfo(servinfo);

上述代码的输出是：

  IPv4: 72.30.38.140
  errno: 2
  IPv4: 72.30.2.43
  errno: 2

错误号 2 是No such file or directory. 我不知道如何解释这个。

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1 回答 1

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错误在这一行：

if (socketfd) {

这应该是：

if (socketfd == -1) {

因为socket()在错误时返回 -1，而不是在成功时返回零（如此处所述：https ://stackoverflow.com/a/1879234/22471 ）

于 2012-03-22T05:14:04.490 回答