问找不到socket.io模块怎么办？

Error: Cannot find module 'socket.io'

at Function.Module._resolveFilename (module.js:547:15)

at Function.Module._load (module.js:474:25)

at Module.require (module.js:596:17)

at require (internal/module.js:11:18)

at Object.<anonymous> (/var/ftp/pub/io-server.js:1:72)

at Module._compile (module.js:652:30)

at Object.Module._extensions..js (module.js:663:10)

at Module.load (module.js:565:32)

at tryModuleLoad (module.js:505:12)

at Function.Module._load (module.js:497:3)

Error: Cannot find module 'socket.io-client'

at Function.Module._resolveFilename (module.js:547:15)

at Function.Module._load (module.js:474:25)

at Module.require (module.js:596:17)

at require (internal/module.js:11:18)

at Object.<anonymous> (/var/ftp/pub/get.js:2:11)

at Module._compile (module.js:652:30)

at Object.Module._extensions..js (module.js:663:10)

at Module.load (module.js:565:32)

at tryModuleLoad (module.js:505:12)

at Function.Module._load (module.js:497:3)

[root@VM_0_8_centos ~]# find / -name socket.io-client

/root/node-v8.11.4-linux-x64/lib/node_modules/socket.io/node_modules/socket.io-client

/root/node_modules/socket.io-client

[root@VM_0_8_centos ~]# find / -name socket.io

/root/node-v8.11.4-linux-x64/lib/node_modules/socket.io

/root/node_modules/socket.io

已经安装了啊，求助....