steam"无法连接到更新服务器"的问题

问题现象如下图所示：

在打开steam游戏时出现了上述问题，无法正常游戏。不光如此steam官网也无法正常显示，只有部分文字和图片，样式缺失。

打开chrome的F12开发者工具，进入network模块监视可发现大量的请求并没有被响应，甚至没有正常请求应有的状态码，但在request Headers中有一个警告信息：Provisional headers are shown。

Provisional headers are shown 的大致意思是由于本机的原因（被屏蔽或者插件的原因），该请求没有实际上被发送出去。在chrome://net-internals/ 中可查看到

右侧的信息详细如下

6053: URL_REQUEST
http://store.akamai.steamstatic.com/public/shared/javascript/jquery-1.8.3.min.js?v=.TZ2NKhB-nliU
Start Time: 2017-11-24 11:56:49.833

t=175962 [st=    0] +REQUEST_ALIVE  [dt=42013]
                     --> priority = "MEDIUM"
                     --> url = "http://store.akamai.steamstatic.com/public/shared/javascript/jquery-1.8.3.min.js?v=.TZ2NKhB-nliU"
t=175962 [st=    0]    URL_REQUEST_DELEGATE  [dt=0]
t=175962 [st=    0]   +URL_REQUEST_START_JOB  [dt=42012]
                       --> load_flags = 33024 (MAYBE_USER_GESTURE | VERIFY_EV_CERT)
                       --> method = "GET"
                       --> url = "http://store.akamai.steamstatic.com/public/shared/javascript/jquery-1.8.3.min.js?v=.TZ2NKhB-nliU"
t=175962 [st=    0]      URL_REQUEST_DELEGATE  [dt=0]
t=175963 [st=    1]      HTTP_CACHE_GET_BACKEND  [dt=0]
t=175963 [st=    1]      HTTP_CACHE_OPEN_ENTRY  [dt=2]
                         --> net_error = -2 (ERR_FAILED)
t=175965 [st=    3]      HTTP_CACHE_CREATE_ENTRY  [dt=5]
t=175970 [st=    8]      HTTP_CACHE_ADD_TO_ENTRY  [dt=0]
t=175971 [st=    9]     +HTTP_STREAM_REQUEST  [dt=42003]
t=175971 [st=    9]        HTTP_STREAM_JOB_CONTROLLER_BOUND
                           --> source_dependency = 6134 (HTTP_STREAM_JOB_CONTROLLER)
t=217974 [st=42012]        HTTP_STREAM_REQUEST_BOUND_TO_JOB
                           --> source_dependency = 6135 (HTTP_STREAM_JOB)
t=217974 [st=42012]     -HTTP_STREAM_REQUEST
t=217974 [st=42012]   -URL_REQUEST_START_JOB
                       --> net_error = -118 (ERR_CONNECTION_TIMED_OUT)
t=217974 [st=42012]    URL_REQUEST_DELEGATE  [dt=1]
t=217975 [st=42013] -REQUEST_ALIVE
                     --> net_error = -118 (ERR_CONNECTION_TIMED_OUT)

由于认识所限，这张表暂时看不懂，但很明显这里出现了问题（~。~）。

分析了一通，问题原因最终定位到hosts文件上。由于本人的机子为了能翻墙访问google，youtube等外网网站，更改了机子上的hosts文件，新hosts文件中有这样一段：

## Steam
2600:1417:a:192::3a7 api.steampowered.com
2600:1417:a:192::3a7 support.steampowered.com
2600:1417:a::174c:cc5b repo.steampowered.com
2600:1417:a::174c:cc5b cdn.akamai.steamstatic.com
2600:1417:a::174c:cc5b store.akamai.steamstatic.com
2600:1417:a::174c:cc5b cdn.store.steampowered.com
2600:1417:a::174c:cc5b cdn.steampowered.com
2600:1417:a::174c:cc5b media.steampowered.com
2600:1417:a::174c:cc5b media4.steampowered.com
2600:1417:a::174c:cc5b content8.steampowered.com
2600:1417:a::174c:cc5b cloud-3.steampowered.com
2600:1417:a::174c:cc5b cloud-3.steamusercontent.com
2600:1417:a::174c:cc5b images.akamai.steamusercontent.com
2600:1417:a::174c:cc5b steamcdn-a.akamaihd.net
2600:1417:a::174c:cc5b steamstore-a.akamaihd.net
2600:1417:a::174c:cc5b steamcommunity-a.akamaihd.net
2600:1417:a::174c:cc5b cdn.steamcommunity.com
2600:1417:a::174c:cc5b store.valvesoftware.com

去掉即可（~。~）

以上，可以正常游戏了，但原因并没有完全弄明白，本文待续。