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[英]How to send server message to specific client in tornado websocket
[英]Send message from server to client after received notification (Tornado+websockets)
我最近開始學習Websocket,並且我決定嘗試學習和使用Python的framweork Tornado創建我的簡單測試項目(沒什么特別的,只是基本項目可以幫助我學習有關Tornado和Websockets的一般知識)。
因此,這是我的想法(工作流程):
1)我收到來自其他應用的http發布請求到我的服務器(例如,有關某人的姓名和電子郵件的信息)
2)我將收到的數據保存到我的postgresql數據庫中,並通知偵聽器(發布/訂閱)新數據已添加到數據庫中
3)接收到通知服務器后,應向客戶端發送消息(write_message方法)
這是我到目前為止的代碼
simple_server.py
import tornado.httpserver
import tornado.ioloop
import tornado.options
import tornado.web
import tornado.websocket
import psycopg2
import psycopg2.extensions
import os
from tornado.options import define, options
define("port", default=8000, help="run on the given port", type=int)
io_loop = tornado.ioloop.IOLoop.instance()
connection = psycopg2.connect('dbname=mydb user=myusername password=mypassword')
connection.set_isolation_level(psycopg2.extensions.ISOLATION_LEVEL_AUTOCOMMIT)
class IndexHandler(tornado.web.RequestHandler):
def get(self):
self.render('index.html')
class ReceivedDataHandler(tornado.web.RequestHandler):
def post(self):
cursor = connection.cursor()
name=self.get_argument('name', 'No name info received')
email = self.get_argument('email', 'No email info received')
self.write("New person with name %s and email %s" %(name, email))
cursor.execute("INSERT INTO mydata VALUES (%s, %s)" %(name, email))
cursor.execute("NOTIFY test_channel;")
class EchoHandler(tornado.websocket.WebSocketHandler):
def open(self):
self.write_message('connected!')
def on_message(self, message):
self.write_message("Received info about new person: "+message)
def on_close(self):
print 'connection closed'
def listen():
cursor = connection.cursor()
cursor.execute("LISTEN test_channel;")
def receive(fd, events):
"""Receive a notify message from channel I listen."""
state = connection.poll()
if state == psycopg2.extensions.POLL_OK:
if connection.notifies:
notify = connection.notifies.pop()
print "New notify message"
io_loop.add_handler(connection.fileno(), receive, io_loop.READ)
if __name__=="__main__":
tornado.options.parse_command_line()
app = tornado.web.Application(
handlers=[
(r'/', IndexHandler),
(r'/person-info', ReceivedDataHandler),
(r'/websocket', EchoHandler)
],
template_path=os.path.join(os.path.dirname(__file__), "templates"),
static_path=os.path.join(os.path.dirname(__file__), "static"),
debug=True
)
http_server = tornado.httpserver.HTTPServer(app)
http_server.listen(options.port)
listen()
io_loop.start()
當我測試通過Postman REST Client發送發帖請求到定義的URL時,一切正常。 數據確實保存到我的數據庫中,並且確實通知偵聽器有新的通知,但是我不知道如何在那之后將消息發送給客戶端。 如果我能做到這一點,那么它將在瀏覽器中顯示該消息,這是我這次要做的全部。
因此,我要做的實際上是在收到有關數據庫中新條目的通知后調用call_message函數(而不是僅打印“ new notify message”),但我只是不知道如何在Tornado中進行操作。 我認為實際上這應該很容易,但是由於我顯然對Tornado(和異步編程)缺乏經驗,所以我一點都沒有堅持。
謝謝你的幫助
最終,我找到了解決該問題的方法。 我剛剛添加了全局變量,在其中添加了所有連接的客戶端,然后在收到通知時向每個連接的客戶端發送消息。 (因為我確實想向所有連接的客戶端發送消息,所以對我來說還可以)
所以這就是現在的樣子
simple_server.py
import tornado.httpserver
import tornado.ioloop
import tornado.options
import tornado.web
import tornado.websocket
import psycopg2
import psycopg2.extensions
import os
from tornado.options import define, options
define("port", default=8000, help="run on the given port", type=int)
io_loop = tornado.ioloop.IOLoop.instance()
connection = psycopg2.connect('dbname=mydb user=myusername password=mypassword')
connection.set_isolation_level(psycopg2.extensions.ISOLATION_LEVEL_AUTOCOMMIT)
# This is a global variable to store all connected clients
websockets = []
class IndexHandler(tornado.web.RequestHandler):
def get(self):
self.render('index.html')
class ReceivedDataHandler(tornado.web.RequestHandler):
def post(self):
cursor = connection.cursor()
name=self.get_argument('name', 'No name info received')
email = self.get_argument('email', 'No email info received')
self.write("New person with name %s and email %s" %(name, email))
cursor.execute("INSERT INTO mydata VALUES (%s, %s)" %(name, email))
cursor.execute("NOTIFY test_channel;")
class EchoHandler(tornado.websocket.WebSocketHandler):
def open(self):
self.write_message('connected!')
def on_message(self, message):
self.write_message("Received info about new person: "+message)
def on_close(self):
print 'connection closed'
def listen():
cursor = connection.cursor()
cursor.execute("LISTEN test_channel;")
def receive(fd, events):
"""Receive a notify message from channel I listen."""
state = connection.poll()
if state == psycopg2.extensions.POLL_OK:
if connection.notifies:
notify = connection.notifies.pop()
for ws in websockets:
ws.write_message("my message")
io_loop.add_handler(connection.fileno(), receive, io_loop.WRITE)
if __name__=="__main__":
tornado.options.parse_command_line()
app = tornado.web.Application(
handlers=[
(r'/', IndexHandler),
(r'/person-info', ReceivedDataHandler),
(r'/websocket', EchoHandler)
],
template_path=os.path.join(os.path.dirname(__file__), "templates"),
static_path=os.path.join(os.path.dirname(__file__), "static"),
debug=True
)
http_server = tornado.httpserver.HTTPServer(app)
http_server.listen(options.port)
listen()
io_loop.start()
可以將其添加到您的EchoHandler.open()方法中:
io_loop.add_handler(connection.fileno(), self.receive, io_loop.READ)
刪除接收函數和另一個io_loop.add_handler調用,然后編寫新版本的接收函數,但使其成為EchoHandler類的實例方法。 這樣,您可以從新的receive方法中調用write_message方法。
諸如此類(未經測試,但希望能闡明我的意思):
class EchoHandler(tornado.websocket.WebSocketHandler):
def open(self):
io_loop.add_handler(connection.fileno(), self.receive, io_loop.READ)
self.write_message('connected!')
def on_message(self, message):
self.write_message("Received info about new person: "+message)
def on_close(self):
print 'connection closed'
def receive(self, fd, events):
"""Receive a notify message from channel I listen."""
state = connection.poll()
if state == psycopg2.extensions.POLL_OK:
if connection.notifies:
notify = connection.notifies.pop()
#print "New notify message"
self.write_message("Your message here")
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