>> import tornado.httpserver  

> import tornado.ioloop  

> import tornado.web  

> from tornado import gen

> from tornado.web import asynchronous

> from tornado.httpclient import AsyncHTTPClient  

> class MainHandler(tornado.web.RequestHandler):  

>     @asynchronous

>     @gen.engine

>     def get(self):

>         http_client = AsyncHTTPClient()

>         self.write("finish")

>         response = yield gen.Task(http_client.fetch,
>> "http://examplay.com",request_timeout=4)

>         if response.error:

>             self.write('except')

>         else :

>             self.write(response.body)

>         self.flush()

>         self.finish()

> settings = {  

>         #"debug": True,  

> }  

> application = tornado.web.Application([  

>     (r"/", MainHandler),  

> ], **settings)  

> if __name__ == "__main__":  

>     http_server = tornado.httpserver.HTTPServer(application)  

>     http_server.listen(8083)  

>     tornado.ioloop.IOLoop.instance().start()