udp_connect函数

#include    <netdb.h>
#include    <stdlib.h>
#include    <unistd.h>
#include    <string.h>
#include    <sys/socket.h>
 
int
udp_connect(const char *host, const char *serv)
{
    int                sockfd, n;
    struct addrinfo    hints, *res, *ressave;
 
    bzero(&hints, sizeof(struct addrinfo));
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_DGRAM;
 
    if ( (n = getaddrinfo(host, serv, &hints, &res)) != ) {
        err_quit (
            "udp_connect error for %s, %s: %s",
            host, serv, gai_strerror(n)
        );
    }
    ressave = res;
 
    do {
        sockfd = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
        if (sockfd < ) {
            continue;    /* ignore this one */
        }
 
        if (connect(sockfd, res->ai_addr, res->ai_addrlen) == ) {
            break;        /* success */
        }
 
        close(sockfd);    /* ignore this one */
    } while ( (res = res->ai_next) != NULL);
 
    if (res == NULL) {    /* errno set from final connect() */
        err_sys("udp_connect error for %s, %s", host, serv);
    }
 
    freeaddrinfo(ressave);
 
    return(sockfd);
}