Socket.IO未定义变量

Question

I am using socket.io to create an interactive graph app. on the server side have a graph variable. When the user loads the page a test event is sent to the server, which sets up the variable and returns it to the users. I have a second event for node dragging, but when i try to drag the node the server says that the graph's nodes and link variables are undefined.

var express = require('express'),
    app = express(),
    http = require('http'),
    socketIo = require('socket.io');
var server = http.createServer(app),
    io = socketIo.listen(server);
var graph = {nodes : [], links : []}

server.listen(8080, function(){
  console.log('server is listening on localhost:8080');
});

app.use(express.static(__dirname + '/'));

io.on('connect', function(socket){

  // dump some test data
  socket.on('test', function(){
    // this just creates a few nodes in an array
    var data = { ... }    
    graph = data;
    io.emit('test', graph);
  });

  socket.on('eventNodeDragStart', function(index){
    console.log('event node drag start: ' + index);

    // undefiend, the graph.nodes is empty here
    console.log(graph.nodes[index] + "\n\n");

    // cannot read property of undefined 
    // also missing error handler on 'socket'
    if(graph.nodes[index].locked) return;

    graph.nodes[index].locked = true;

    io.emit('eventNodeDragStart', index);
  });
});

Answer 1

Solved the problem by replacing this line:

io.on('connect', function(socket){

with this:

io.sockets.on('connect', function(socket){

Not sure why it works, but it does.