install socket.io on ubuntu
You're trying to install it without a package.json file, and in your solution you installed it globally, which is usually not what you want for socket.io.
Instead, you should include a package.json file in your working directory and either run:
> npm install socket.io --savewhich will automatically append it to package.json, or your you can physically include it in the dependencies and then just run:
> npm install