nginx - 502 错误网关 nginx 虚拟机

Question

我的 VM 网络服务器上出现 502 Bad Gateway，但我不知道该怎么办。运行 pm2 日志时收到的错误消息如下。

/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)

我还收到此错误消息“从上游读取响应标头时上游过早关闭连接”