c - socket编程中getaddrinfo函数的困惑

Question

在 getaddrinfo("www.example.net","1234", &hints, &server_info)

hints参数有什么用？

Answer 1

getaddrinfo 记录在 man page 中，其中关于提示参数有这样的说法:

The hints argument points to an addrinfo structure that specifies criteria for selecting the socket address structures returned in the list pointed to by res. If hints is not NULL it points to an addrinfo structure whose ai_family, ai_socktype, and ai_protocol specify criteria that limit the set of socket addresses returned by getaddrinfo()

所以它是一个根据给定标准限制结果的参数。使用 addrinfo 结构给出标准:

struct addrinfo {
    int              ai_flags;
    int              ai_family;
    int              ai_socktype;
    int              ai_protocol;
    socklen_t        ai_addrlen;
    struct sockaddr *ai_addr;
    char            *ai_canonname;
    struct addrinfo *ai_next;
};

您可以在同一手册页上了解该结构体的每个参数。