这个是实现长轮询的代码。客户端使用的是coffeescript，服务器是Python的Flask。

long-polling-demo.coffee

Post =
  getId: ->
        $.ajax {
                type: 'POST'
                url: '/getId'
                context: $('body')
                success: (data) ->
                  successHandle(data)
                  return
                error: (xhr, type) ->
                        console.log xhr, type
                        return 
                }
        return    

# Success Handle
successHandle = (data) ->
        console.log data.u_id
        $('#show').append(data.u_id)
        Post.getId()
        return

# after loading run the below codes
$ ->
  Post.getId()
  return 

long-polling-demo.py

from flask import Flask, session, redirect, url_for, escape, request, render_template, jsonify
import os
import random
import time

# app = Flask(__name__)
app = Flask(__name__, 
            # static_path='/static', 
            static_folder='static',
            template_folder='templates')

@app.route('/')
def index():
    
    if 'username' in session:
        return render_template('logged.html',
                number = random.random(),
                username = escape(session['username']),)
    return render_template('index.html')

@app.route('/login', methods=['GET', 'POST'])
def login():
    """
    """
    if request.method == 'POST':
        session['username'] = request.form['username']
        return redirect(url_for('index'))

    return render_template('login.html')

@app.route('/logout')
def logout():
    # remove the username from the session if it's there
    session.pop('username', None)
    return redirect(url_for('index'))

# set the secret key.  keep this really secret:
app.secret_key = 'A0Zr98j/3yX R~XHH!jmN]LWX/,?RT'

@app.route('/getId', methods=['GET', 'POST'])
def getId():
    while True:
        time.sleep(3)
        msg = jsonify(u_id = '100')
        return msg
    
# with app.app_context():
      # url_for('static', filename='zepto.min.js')
    
if __name__ == '__main__':
    app.debug = True
    app.run()