问题描述
在之前的一篇博文中，介绍了在App Service中抓取网络日志：
- 抓取Windows的网络包：【应用服务 App Service】App Service中抓取网络日志
- 抓取Linux的网络包：【Azure 应用服务】App Service For Linux 如何在 Web 应用实例上住抓取网络日志
现在，随着App Service的更新，Linnx也可以直接登录到SSH而不在需要复杂的配置操作。同时Windows环境中，也不在需要在本地安装 armclient.exe工具，而是直接通过 App Service的门户完成抓取，下载操作。
操作步骤
第一步: 进入App Service的Overview页面，点击“Diagnose and solve problems”, 然后再选择“ Diagnostic Tools” 方块
(注意： Diagnostic Tools路径变动，查看下图中的步骤）
第二步：选择 Collect Network Trace , 并设定抓取日志的时间长度， 60秒 ~ 15分钟的值供选择。页面中也对抓取网络日志的情况进行了说明：
Collect a Network Trace
If your app is facing issues while connecting to a remote server, you can use this tool to collect a network trace on the instance(s) serving the Web App.
Analyzing network traces is complex and time consuming task. Before collecting a network trace, please make sure you understand that you really need to collect a network trace to troubleshoot the problem.
What you should know before collecting a Network Trace
- 网络日志帮助定位TCP丢包，检查App Service与其他服务之间的HTTP通信情况（Network traces are helpful to troubleshoot TCP packet loss and to check HTTP communication that your App is making with the remote endpoints.）
- 在开始抓取网络日志后，要在App Service上重新我们需要抓包解决的问题（After the network trace is started, you should reproduce the problem so that outbound traffic from your App gets captured in the trace.)
- 如果适用HTTPS，那么数据将被加密(If the remote endpoints are called over TLS or SSL (i.e. HTTPS), then the traffic in the trace will be encrypted.）
- 将会收集应用所在的全部实例上的网络包（Network traces are collected on all the instance(s) serving your App.)
- 抓取网络日志只包含当前正在运行进程。当抓取网络包开始后，新的进程的网络包将不被抓取(Traces are captured only of processes that are running when the trace is started. The trace does not capture packets of any processes that start after the capture is started.)
- 可以适用Network Monitor和Wireshark工具对网络包进行分析（To analyze the Network Trace, you need tools like Network Monitor or Wireshark that can open the network captures.）
第三步：等待抓取时间完成，页面会直接显示网络包的下载地址。点击即可。
PS：此处不需要在登录到Kudu站点中，到 c:\home\logfiles\networktrace 目录中进行下载，但是如果要查看历史的网络抓包文件，还是需要到Kudu站点中下载。
注意：当前App Service For Linux环境，还是不支持以上方式抓包。 需要SSH，然后执行以下命令：
tcpdump -i any host <your app service inbound ip address> and tcp port 443 -n -v -s 0 -w /tmp/appnetworktrace.pcap
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