gethostbyname alarm超时处理

在使用gethostbyname DNS查询的时候，处理很慢的情况。使用alarm设置超时时间，并用setjmp进行处理。

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#define EXIT_SUCC	exit(0);
#define	EXIT_FAIL	exit(-1);
#define TIME_OUT	3
jmp_buf	ebuf;
void handler()
{
    longjmp(ebuf,1);
}
int main(int argc, char **argv)
{
    char		*hostname;
    char		buff[]="request msg";
    struct 		sockaddr_in sevaddr;
    int		sockfd, port, iBytes;
    struct		hostent *host;
    if(argc != 3) {
        printf("Usage: %s  n", argv[0]);
        EXIT_SUCC;
    }
    if(setjmp(ebuf)) {
        printf("gethostbyname timeoutn");
        exit(1);
    }
    hostname = argv[1];
    port	 = atoi(argv[2]);
    signal(SIGALRM, handler);
    alarm(TIME_OUT);
    if((host = gethostbyname(hostname)) == NULL) {
        perror("gethostbyname");
        EXIT_FAIL;
    }
    alarm(0);
    if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        perror("socket:");
        EXIT_FAIL;
    }
    memset(&sevaddr, 0x00, sizeof(struct sockaddr_in));
    sevaddr.sin_family = AF_INET;
    sevaddr.sin_addr = *((struct in_addr *)host->h_addr);
    sevaddr.sin_port = htons(port);
    printf("connect to remote server ....n");
    if(connect(sockfd, (struct sockaddr *)&sevaddr, sizeof(struct sockaddr_in)) == -1) {
        perror("connect");
        EXIT_FAIL;
    }
    iBytes = send(sockfd, buff, strlen(buff), 0);
    if(iBytes < 0) {
        perror("send");
        EXIT_FAIL;
    }
    printf("Send Data :len[%d]buff[%s]n", iBytes, buff);
    close(sockfd);
    EXIT_SUCC;
}