根据域名获取IP地址,并探测是否可达

/*
　　Author　　:decwang@2014.09.01
　　Mail　　  :deworks@sina.com
*/
#define PRINTLOG printf
//返回0表示成功,其他为失败.
int getIpAddressByGetAddrInfo(const char* address,char* realIP,int maxLen)
{
    if (NULL == address || NULL == realIP)
    {
        PRINTLOG("param address wrong
");
        return -1;
    }
    struct addrinfo *answer = NULL, hint, *curr = NULL;
    bzero(&hint, sizeof(hint));
    hint.ai_family = AF_INET;
    hint.ai_socktype = SOCK_STREAM;
    int ret = getaddrinfo(address, NULL, &hint, &answer);
    if (ret != 0)
    {
        PRINTLOG("error on getaddrinfo: ret: %s
",gai_strerror(ret));
        return -2;
    }
    for (curr = answer; curr != NULL; curr = curr->ai_next)
    {
        inet_ntop(AF_INET,&(((struct sockaddr_in *)(curr->ai_addr))->sin_addr),realIP, maxLen);
        PRINTLOG("realIP is %s
", realIP);
        break;
    }
    freeaddrinfo(answer);
    return 0;
}
//返回1表示网络可达,返回其他为失败
int isReachable(const char* address,int port,int timeout)
{
    if (NULL == address)
    {
        PRINTLOG("param address wrong
");
        return -1;
    }
    if (timeout <= 0)
    {
        PRINTLOG("param timeout wrong
");
        return -1;        
    }
    struct sockaddr_in    server_addr;    
    char realIP[128];
    memset(realIP,0,sizeof(realIP));
    int nRet = getIpAddressByGetAddrInfo(address, realIP, 128-1);
    if (nRet != 0)
    {
        PRINTLOG("get real ip address failed
");
        return -1;
    }
    if (port >= 65535 || port <= 0)
    {
        PRINTLOG("port invalid
");
        return -1;
    }
    
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if(sockfd < 0) 
    {
        PRINTLOG("create socket failed
");
        return -2;
    }
    
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(port);
    server_addr.sin_addr.s_addr = inet_addr(realIP);
    
    int error=-1, len;
    len = sizeof(int);
    struct timeval tm;
    fd_set set;
    fcntl(sockfd, F_SETFL, O_NONBLOCK);
if( connect(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) ==-1)
    {
        tm.tv_sec = timeout;
        tm.tv_usec = 0;
        FD_ZERO(&set);
        FD_SET(sockfd, &set);
        if( select(sockfd+1, NULL, &set, NULL, &tm) > 0)
        {
            getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &error, (socklen_t *)&len);
            if(error == 0) 
                nRet = 1;
            else 
                nRet = 0;
        } 
        else 
            nRet = 0;
    }
    else 
        nRet = 1;
    close( sockfd );        
    return nRet;
}

这段代码是为了修正之前的iOS上的双网络连接探测用的,之前的SCNetWork对网络的状态判断存在,故干脆采用直接连接的方式进行判断