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1、c-ares是一个实现的DNS非阻塞异步解析，libcurl, libevent, gevent, nodejs wireshark都使用了c-ares，因此在一般开发一些服务的客户端Client，在连接服务器Server时，需要做的工作的就是域名解析。

2、源码下载路径： 

3、编译使用

    （1）Win32环境

      源码下载解压后，进入vs文件夹，使用VS2013等工具打开工程，即可以编译Win32的caresd.lib和caresd.dll

static int CloudServerHostIsIP(const char * serverhost){	struct in_addr addr;	int lsuccess;	lsuccess= inet_pton(AF_INET, serverhost, &addr);	return lsuccess> 0 ? 0 : -1;}static void DNSCallBack(void* arg, int status, int timeouts, struct hostent* host){	char **lpSrc;	char  * lpHost = (char *)arg;	if (status == ARES_SUCCESS)	{		for (lpSrc = host->h_addr_list; *lpSrc; lpSrc++)		{			char addr_buf[32] = "";			ares_inet_ntop(host->h_addrtype, *lpSrc, addr_buf, sizeof(addr_buf));			if (strlen(addr_buf) != 0)			{				strcpy(lpHost, addr_buf);				break;			}		}	}}static int DomainNameReSolution(const char * lpDomainName, char * lpHost){	int lsuccess= 0;	ares_channel channel;	lsuccess= ares_library_init(ARES_LIB_INIT_ALL);	if ((lsuccess= ares_init(&channel)) != ARES_SUCCESS) return -1;	int trytime = 3;	do{		fd_set readers, writers;		timeval tv;		tv.tv_sec = 5;		tv.tv_usec = 0;		FD_ZERO(&readers);		FD_ZERO(&writers);		ares_gethostbyname(channel, lpDomainName, AF_INET, DNSCallBack, (char *)lpHost);		int nfds = ares_fds(channel, &readers, &writers);		if (nfds == 0){			continue;		}		int count = select(nfds, &readers, NULL, NULL, &tv);		if (count > 0){			ares_process(channel, &readers, &writers);			lsuccess= 0;			break;		}		else{			lsuccess= -1;		}	} while (trytime-- > 0);	ares_destroy(channel);	ares_library_cleanup();	return lsuccess;}

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