11.11 host_serv Function
Our first interface to getaddrinfo does
not require the caller to allocate a hints structure and fill it in. Instead, the
two fields of interest, the address family and the socket type, are
arguments to our host_serv function.
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#include "unp.h"
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struct addrinfo *host_serv (const char
*hostname, const char
*service, int
family, ints socktype);
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Returns: pointer to addrinfo structure
if OK, NULL on error
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Figure
11.9 shows the source code for this function.
Figure 11.9
host_serv function.
lib/host_serv.c
1 #include "unp.h"
2 struct addrinfo *
3 host_serv(const char *host, const char *serv, int family, int socktype)
4 {
5 int n;
6 struct addrinfo hints, *res;
7 bzero (&hints, sizeof (struct addrinfo));
8 hints.ai_flags = AI_CANONNAME; /* always return canonical name */
9 hints.ai_family = family; /* AF_UNSPEC, AF_INET, AF_INET6, etc. */
10 hints.ai_socktype = socktype; /* 0, SOCK_STREAM, SOCK_DGRAM, etc. */
11 if ( (n = getaddrinfo(host, serv, &hints, &res)) != 0)
12 return (NULL);
13 return (res); /* return pointer to first on linked list */
14 }
7鈥?3
The function initializes a hints
structure, calls getaddrinfo, and returns a null pointer
if an error occurs.
We will call this function from Figure
16.17 when we want to use getaddrinfo to obtain the
host and service information, but we want to establish the
connection ourself.
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