TypeError: Cannot call method 'on' of undefined

[kpbird]

listen on port 8080
info - socket.io started

node.js:201
throw e; // process.nextTick error, or 'error' event on first tick
^
TypeError: Cannot call method 'on' of undefined
at Object.listen (/Users/ketanparmar/Documents/ngrid.js:14:19)
at Object. (/Users/ketanparmar/Documents/njsgrid/examples/wordcount/app.js:4:7)
at Module._compile (module.js:432:26)
at Object..js (module.js:450:10)
at Module.load (module.js:351:31)
at Function._load (module.js:310:12)
at Array.0 (module.js:470:10)
at EventEmitter._tickCallback (node.js:192:40)

[3rd-Eden]

Socket.IO started, and the stacktrace points to your own ngrid.js. So I'm closing this as it's your application that is throwing an error, not socket.io

[kpbird]

Thank you for response, I have resolve the problem.