回复 第1楼 的 bayeswhu：
getURL 有个参数
<br />
async: a logical value that determines whether the download request<br />
should be done via asynchronous,concurrent downloading or a<br />
serial download. This really only arises when we are trying<br />
to download multiple URIs in a single call. There are<br />
trade-offs between concurrent and serial downloads,<br />
essentially trading CPU cycles for shorter elapsed times.<br />
Concurrent downloads reduce the overall time waiting for<br />
'getURI'/'getURL' to return.<br />
</p>
即使并发请求，一般也要限制访问服务器的并发数量不要过于庞大，否则就变成一种flood了。
