blocks|key|1433419|text|在微软的支持下，我们能够指出问题所在。这里为我的社区和我的未来做一些概述。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1433420|连接在三路握手过程中被中断。|1433421|packet+|1433422|客户端发送SYN数据包|unordered-list-item|1433423|+sql实例与ACK+SYN+|1433424|响应经过几次未成功的尝试后，实例发送了重置|1433425|1433426|1433427|1433428|1433429|​|1433430|网络|1433431|service|1433432|6.x.x.18+|1433433|x.x.224.8应用程序|1433434|1433435|1433436|数据包|1433437|SYNC|1433438|RESET|1433439|
+|1433440|SYN+|ordered-list-item|1433441|ACK|1433442|1433443|1433444|📷|atomic|offset|length|1433445|1433446|在我们的情况下，SYN.ACK似乎被一个网络设备丢弃了。|1433447|有了wireshark，就可以看到设备的MAC地址删除ACK+SYN。在此之后，我们发现了一个点对点的天蓝色VPN+(https://learn.microsoft.com/en-us/azure/vpn-gateway/point-to-site-about)的缺失路径。|1433448|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://developer.qcloudimg.com/http-save/yehe-900000/10a7e49a9f91bc1c561321259099efaf.png|imageAlt|1|LINK|MUTABLE|url|https://learn.microsoft.com/en-us/azure/vpn-gateway/point-to-site-about^0|0|0|0|0|1|2|2|1|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|1|0|0|0|0|1N|1Z|1|0^^$0|@$1|2|3|4|5|6|7|25|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|26|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|27|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|28|8|@]|9|@]|A|$]]|$1|I|3|J|5|H|7|29|8|@]|9|@]|A|$]]|$1|K|3|L|5|H|7|2A|8|@]|9|@]|A|$]]|$1|M|3|-4|5|H|7|2B|8|@]|9|@]|A|$]]|$1|N|3|-4|5|6|7|2C|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|2D|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|2E|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|2F|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|2G|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|2H|8|@]|9|@]|A|$]]|$1|W|3|X|5|H|7|2I|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|H|7|2J|8|@]|9|@]|A|$]]|$1|10|3|-4|5|6|7|2K|8|@]|9|@]|A|$]]|$1|11|3|-4|5|6|7|2L|8|@]|9|@]|A|$]]|$1|12|3|13|5|6|7|2M|8|@]|9|@]|A|$]]|$1|14|3|15|5|6|7|2N|8|@]|9|@]|A|$]]|$1|16|3|17|5|H|7|2O|8|@]|9|@]|A|$]]|$1|18|3|19|5|6|7|2P|8|@]|9|@]|A|$]]|$1|1A|3|1B|5|1C|7|2Q|8|@]|9|@]|A|$]]|$1|1D|3|1E|5|1C|7|2R|8|@]|9|@]|A|$]]|$1|1F|3|-4|5|6|7|2S|8|@]|9|@]|A|$]]|$1|1G|3|R|5|6|7|2T|8|@]|9|@]|A|$]]|$1|1H|3|1I|5|1J|7|2U|8|@]|9|@$1K|2V|1L|2W|1|2X]]|A|$]]|$1|1M|3|R|5|6|7|2Y|8|@]|9|@]|A|$]]|$1|1N|3|1O|5|6|7|2Z|8|@]|9|@]|A|$]]|$1|1P|3|1Q|5|6|7|30|8|@]|9|@$1K|31|1L|32|1|33]]|A|$]]|$1|1R|3|-4|5|6|7|34|8|@]|9|@]|A|$]]]|1S|$1T|$5|1U|1V|1W|A|$1X|1Y|1Z|-4]]|20|$5|21|1V|22|A|$23|24]]]]

with support of microsoft, we were able to pin point the issue. here some recap for the community and my future me.

connection was interrupted during the 3 way handshake process

<ul>
<li>client send a SYN packet</li>
<li>sql instance respond with ACK SYN

<ul>
<li>after several unsuccesful attempts, sql instance send a RESET packet</li>
</ul></li>
</ul>

network

<ul>
<li>x.x.224.8 app service</li>
<li>6.x.x.18 sql server</li>
</ul>

packets

<ol>
<li>SYN </li>
<li>ACK SYNC</li>
<li>RESET</li>
</ol>

<a href="https://i.stack.imgur.com/nKoGM.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/nKoGM.png" alt="enter image description here"></a>

in our situation, the SYN.ACK seemed to be dropped by a network device

with wireshark, it was then possible to see the MAC address of the device dropping the ACK SYN. 
following the breabcrumb from there allowed us to spot a missing route for a point-to-site azure VPN (<a href="https://learn.microsoft.com/en-us/azure/vpn-gateway/point-to-site-about" rel="nofollow noreferrer">https://learn.microsoft.com/en-us/azure/vpn-gateway/point-to-site-about</a>)

<blockquote>
 The timeout period elapsed while attempting to consume the pre-login
 handshake acknowledgement
 This could be because the pre-login handshake failed or the server was
 unable to respond back in time. The duration spent while attempting
 to connect to this server was - [Pre-Login] initialization=30;
 handshake=15004; The wait operation timed out
</blockquote>

infamous pre-login error. it worked before in the same environment and suddenly stopped, pretty sure it's a side effect at database vm level, looking for ideas for investigation before pinging microsoft with premier tickets. our firewall team, even by monitoring didn't spotted any loophole.

context

<ul>
<li>azure app service windows (appservice) : connection worked for months</li>
<li>appservice webjob toward an mssql database (databaseA) hosted on a vm in azure</li>
<li>appservice connected to a vnet</li>
<li>appservice able to connect to other databases (mssql in private datacenter)</li>
<li>webjob &amp; ssms to databaseA working from local dev laptop</li>
<li>database on static 1433</li>
</ul>

<a href="https://i.stack.imgur.com/naArd.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/naArd.png" alt="enter image description here"></a>

<ul>
<li>successful tcpping on azure console</li>
</ul>

<a href="https://i.stack.imgur.com/YFw9u.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/YFw9u.png" alt="enter image description here"></a>

any idea where to find more detailled log which could explained the problem.

The underlying provider failed on Open. Connection Timeout Expired

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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诚挚邀请您参与本次调研，分享您的真实使用感受与建议。您的反馈至关重要，感谢您的支持与参与！

社区新版编辑器体验调研

在尝试使用登录前握手确认时，超时时间已经过去，这可能是因为登录前握手失败或服务器无法及时响应。试图连接到此服务器时所花费的时间是-Pre initialization=30；handshake=15004；等待操作超时。臭名昭著的预登录错误。它以前在相同的环境中工作过，突然停止了，非常肯定这是数据库vm级的一个副作用，在给微软买高级票之前，它正在寻找调查的思路。我们的防火墙小组，即使通过监控，也没

问基础提供程序在打开时失败。连接超时过期
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