update faq.md

Author: hengyunabc

site/docs/doc/faq.md

@@ -8,6 +8,28 @@
 
 日志文件路径： `~/logs/arthas/arthas.log`
 
+
+### telnet: connect to address 127.0.0.1: Connection refused
+
+1. 检查日志 `~/logs/arthas/arthas.log`
+2. 检查`as.sh`/`arthas-boot.jar` 的启动参数，是否指定了特定的`port`
+3. 用`netstat` 检查`LISTEN 3658` 端口的进程，确认它是`java`进程，并且是想要诊断的进程
+4. 如果`LISTEN 3658` 端口的进程不是 `java` 进程，则`3658`端口已经被占用。需要在`as.sh`/`arthas-boot.jar` 的启动参数指定其它端口。
+5. 确认进程和端口后，尝试用`telnet 127.0.0.1 3658`去连接
+
+
+本质上`arthas`会在应用java进程内启动一个`tcp server`，然后使用`telnet`去连接它。
+
+1. 可能端口不匹配
+2. 可能进程本身已经挂起，不能接受新连接
+
+
+如果Arthas 日志里有 `Arthas server already bind.`
+
+1. 说明`Arthas server`曾经启动过，检查目标进程打开的文件描述符。如果是`linux`环境，可以去 `/proc/$pid/fd` 下面，使用`ls -alh | grep arthas`，检查进程是否已加载`arthas`相关的 jar 包。
+2. 如果没有，那么可能已启动`arthas`的是其它进程，也可能应用已经重启过了。
+
+
 ### Arthas attach 之后对原进程性能有多大的影响
 
 [https://github.com/alibaba/arthas/issues/44](https://github.com/alibaba/arthas/issues/44)

site/docs/en/doc/faq.md

@@ -8,6 +8,25 @@ For questions that are not in this list, please search in issues. [https://githu
 
 Log file path: `~/logs/arthas/arthas.log`
 
+
+### telnet: connect to address 127.0.0.1: Connection refused
+
+1. Check the log `~/logs/arthas/arthas.log`
+2. Check the startup parameters of `as.sh`/`arthas-boot.jar`, whether a specific `port` is specified
+3. Use `netstat` to check the process of `LISTEN 3658` port, confirm it is a `java` process, and it is the process you want to diagnose
+4. If the process of `LISTEN 3658` port is not a `java` process, then the `3658` port is already occupied. You need to specify other ports in the startup parameters of `as.sh`/`arthas-boot.jar`.
+5. After confirming the process and port, try to connect with `telnet 127.0.0.1 3658`
+
+Essentially, `arthas` will start a `tcp server` within the application java process, and then use `telnet` to connect to it.
+
+1. The port may not match
+2. The process itself may have been suspended and cannot accept new connections
+
+If there is `Arthas server already bind.` in the Arthas log
+
+1. It means that the `Arthas server` has been started before, check the file descriptors opened by the target process. If it is a `linux` environment, you can go to `/proc/$pid/fd`, use `ls -alh | grep arthas` to check whether the process has loaded the `arthas` related jar package.
+2. If not, it may be that other processes have started `arthas`, or the application has been restarted.
+
 ### How much impact does Arthas attach have on the performance of the original process?
 
 [https://github.com/alibaba/arthas/issues/44](https://github.com/alibaba/arthas/issues/44)