fiddler2跟踪结果如下：
ClientConnected: 19:35:18.284
ClientBeginRequest: 19:35:18.284
GotRequestHeaders: 19:35:18.284
ClientDoneRequest: 19:35:18.284
Determine Gateway: 0ms
DNS Lookup: 0ms
TCP/IP Connect: 21021ms
HTTPS Handshake: 0ms
ServerConnected: 19:35:39.306
FiddlerBeginRequest: 00:00:00.000
ServerGotRequest: 00:00:00.000
ServerBeginResponse: 00:00:00.000
GotResponseHeaders: 00:00:00.000
ServerDoneResponse: 00:00:00.000
ClientBeginResponse: 19:35:39.314
[Fiddler] The socket connection to 210.xx.xx.xxx failed. <br />ErrorCode: 10060. <br />由于连接方在一段时间后没有正确答复或连接的主机没有反应，连接尝试失败。 210.xx.xx.xxx:80
换VPN内网地址访问没有问题，外网访问在并发大的情况下报这个错误，是不是防火墙拦截了？可是客户说防火墙没拦截。。。
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