我的VM网络服务器上有一个502 Bad Gateway，我不知道该怎么做 . 运行pm2日志时，我得到的错误消息如下 .
/root/.pm2/logs/server-error-0.log last 15 lines:
0|server | at Object.Module._extensions..js
(internal/modules/cjs/loader.js:713:10)
0|server | at Module.load (internal/modules/cjs/loader.js:612:32)
0|server | at tryModuleLoad
(internal/modules/cjs/loader.js:551:12)
0|server | at Function.Module._load
(internal/modules/cjs/loader.js:543:3)
0|server | Error: listen EADDRINUSE :::9000
0|server | at Server.setupListenHandle [as _listen2]
(net.js:1330:14)
0|server | at listenInCluster (net.js:1378:12)
0|server | at Server.listen (net.js:1466:7)
0|server | at Function.listen
(/var/www/wsApp/client/node_modules/express/lib/application.js:618:24)
0|server | at Object.<anonymous>
(/var/www/wsApp/client/server.js:22:5)
0|server | at Module._compile
(internal/modules/cjs/loader.js:702:30)
0|server | at Object.Module._extensions..js
(internal/modules/cjs/loader.js:713:10)
0|server | at Module.load (internal/modules/cjs/loader.js:612:32)
0|server | at tryModuleLoad
(internal/modules/cjs/loader.js:551:12)
0|server | at Function.Module._load
(internal/modules/cjs/loader.js:543:3)
我也从上游读取响应头时收到此错误消息'上游过早关闭连接'