node error cannot find module already installed

[root@zexu websocket_start]# npm ls -g installed
npm WARN ls doesn't take positional args. Try the 'search' command
npm WARN websocket-server@1.4.04 package.json: bugs['web'] should probably be bugs['url']
/usr/lib
├─┬ npm@1.1.2 
│ ├── abbrev@1.0.3 
│ ├── block-stream@0.0.5 
│ ├── fast-list@1.0.2 
│ ├── fstream@0.1.12 
│ ├── graceful-fs@1.1.5 
│ ├── inherits@1.0.0 
│ ├── ini@1.0.2 
│ ├── lru-cache@1.0.5 
│ ├── minimatch@0.1.5 
│ ├── mkdirp@0.3.0 
│ ├── node-uuid@1.3.3 
│ ├── nopt@1.0.10 
│ ├── proto-list@1.0.0 
│ ├── read@0.0.1 
│ ├── request@2.9.151 
│ ├── rimraf@2.0.1 
│ ├── semver@1.0.13 
│ ├── slide@1.1.3 
│ ├── tar@0.1.12 
│ └── which@1.0.3 
└── websocket-server@1.4.04 
[root@zexu websocket_start]# npm ls  installed
npm WARN ls doesn't take positional args. Try the 'search' command
/home/qonco/workspace/JS/websocket_start
(empty)
[root@zexu websocket_start]# node
> require("websocket-server");
Error: Cannot find module 'websocket-server'
    at Function._resolveFilename (module.js:332:11)
    at Function._load (module.js:279:25)
    at Module.require (module.js:354:17)
    at require (module.js:370:17)
    at repl:1:1
    at REPLServer.eval (repl.js:80:21)
    at repl.js:190:20
    at REPLServer.eval (repl.js:87:5)
    at Interface. (repl.js:182:12)
    at Interface.emit (events.js:67:17)
>

回答1:

Have you installed the module with the -g option? I think that not every module is meant to be installed globally, instead, try installing it locally for the project you are creating (npm install), and check if the error persists.

回答2:

you have installed the module global go to your app and try this to link the global to your application folder