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WebSocket for Dummies
Bartosz Zaczyńskibartosz.zaczynski@grandparade.co.uk
TCP/IP Socket
http://www.freeimages.co.uk/
Protocol
http://www.freeimages.co.uk/
Protocol: telnet
Protocol: HTTP
Protocol: HTTPS
Protocol: fixed length message
Protocol: message delimiter
Example: Betradar TCP/SSL
@tornado.gen.coroutinedef receive(self): """Read CRLF-delimited messages and push them onto the queue.""" try: if not self.iostream.closed():
message_body = yield self.iostream.read_until('\r\n\r\n')
logger.debug('Received message: %s', message_body.strip())
received_at = datetime.datetime.utcnow() message = parser.parse(message_body, received_at)
if message is not None: if self.is_whitelisted(message): self.messages.enqueue(message) self.log(message)
self.ioloop.add_callback(self.receive)
except tornado.iostream.StreamClosedError:
if not self._closing: logger.error('Betradar connection closed by remote endpoint')
self.heartbeat.stop()
if self.on_closed: self.on_closed()
WebSocket: handshake
WebSocket: server frame
WebSocket: client frame
WebSocket: JavaScript API
<!DOCTYPE html><html><head> <title>WebSocket Demo</title> <script> var ws = new WebSocket("ws://localhost:8080/websocket");
ws.onopen = function(event) { console.log("open"); }; ws.onclose = function(event) { console.log("closed"); }; ws.onerror = function(event) { console.log("error"); }; ws.onmessage = function(event) { console.log(event.data); };
function onButtonClick() { ws.send(document.getElementById("message").value) } </script></head><body> <input type="text" id="message"> <button type="button" onclick="onButtonClick();">Send</button></body></html>
WebSocket: JavaScript libs
var ws = STOMP.over(new SockJS("/websocket"));
var ws = io.connect("http://localhost:8080/websocket");
UNSUBSCRIBE
id:sub-0
\u0000
SUBSCRIBEid:sub-0destination:/topic/chat.all\u0000
WebSocket: sub protocol
CONNEC
T
accept
-versi
on:1.1
,1.0
heart-
beat:1
0000,1
0000
\u0000
CONNECTEDversion:1.1heart-beat:0,0\u0000
MESSAGEsubscription:sub-0message-id:007destination:/topic/chat.allcontent-type:text/plaincontent-length:11
hello world\u0000
SENDdestination:/topic/chat.all
content-type:text/plainhello world\u0000
Debugging
Summary
1. Lightweight binary protocol on top of TCP.
2. Different from HTTP (except for the handshake).
3. Replaces AJAX polling and plugins such as Flash.
Q&A
Bartosz Zaczyńskibartosz.zaczynski@grandparade.co.uk
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