原因：
如果开启了IPv6，curl默认会优先解析 IPv6，在对应域名没有 IPv6 的情况下，会等待 IPv6 dns解析失败 timeout 之后才按以前的正常流程去找 IPv4。在程序中我对curl获取内容都作了较为严格的超时限制，所以就会造成无法获取内容的问题。
解决方法：设置默认访问为ipv4。
php的curl设置方法如下：
<?<span php><span><span ipv6 edit by www.jbxue.com><span>
<span> =<span curl_init curl_setopt><span>, CURLOPT_URL, <span><span curl_setopt><span>, CURLOPT_RETURNTRANSFER, <span true><span><span><span>
<span if>(<span defined>('CURLOPT_IPRESOLVE') && <span defined>('CURL_IPRESOLVE_V4'<span curl_setopt><span>, CURLOPT_IPRESOLVE,<span curl_ipresolve_v4><span><span>
curl_setopt (<span>, CURLOPT_CONNECTTIMEOUT, <span><span><span><span>
curl_setopt (<span>, CURLOPT_TIMEOUT,<span>*3<span><span> = curl_exec(<span><span curl_close><span>);</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>
注：curl_setopt($ch, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4) 只有在php版本5.3及以上版本，curl版本7.10.8及以上版本时，以上设置才生效。
