Re: Django Channels - Class Based Consumers

The stream is the name of the stream inside the Multiplexer - it's like a sub-channel inside the WebSocket that is used by either end to distinguish packets from each other (it's why you provide it to the JavaScript binding - it needs to know which stream to listen to)

Andrew

On Wed, Apr 5, 2017 at 9:15 AM, Dan Alderman <daniel.thomas.alderman@gmail.com> wrote:

Hi Andrew,

Many thanks for your input - that does indeed help.

What was really confusing me was what arguments I actually needed to supply to the JsonWebsocketConsumer.group_send() function.

Not fully understanding classmethods, I was trying to pass the cls argument as well.

I understand what the group_name and payload arguments do - but what s the stream argument doing?

Dan

On Tuesday, 4 April 2017 13:57:07 UTC+1, Andrew Godwin wrote:

Hi Dan,

An initial glance shows that you might be passing the arguments wrong to Multiplexer.group_send(group_name, stream, payload) - I'm not sure why you are using multiplexer.__class__.__name__ as the group name, but the group name you configured in connection_groups is updatedb_results, and the stream you're listening to in the JS client is also updatedb_results, so you should set both of these to that value.

Andrew

On Tue, Apr 4, 2017 at 9:55 AM, Dan Alderman <daniel.thom...@gmail.com> wrote:

Hi guys,

Been trying to get my head around this for ages now but still no luck, hopefully someone can point me in the right direction.

I'm trying to set up a Demultiplexer with a JsonWebsocketConsumer that sends to a group. (There is only one stream in the Demultiplexer at the moment, but I intend to add more).

The prints in each of the functions work when I interact with my app in the web browser, but I'm having trouble getting a response in the browser via websockets.

If I user multiplexer.send() then it works, but it only goes to a single connection (as you'd expect).

consumers.py

from channels.generic.websockets import JsonWebsocketConsumer, WebsocketDemultiplexer

class DatabaseUpdateConsumer(JsonWebsocketConsumer):
strict_ordering = True

def connection_groups(self, **kwargs):
return ["updatedb_results"]

def connect(self, message, multiplexer, **kwargs):
print "Connected!"
multiplexer.group_send(multiplexer.__class__.__name__, self.connection_groups(), {'text': "Connected!"})

def disconnect(self, message, multiplexer, **kwargs):
print("Stream %s is closed" % multiplexer.stream)

def receive(self, content, multiplexer, **kwargs):
print "Message received by server!"
multiplexer.group_send(multiplexer.__class__.__name__, self.connection_groups(), {'text': "Message received by server!"})

class Demultiplexer(WebsocketDemultiplexer):

consumers = {
"updatedb_results": DatabaseUpdateConsumer,
}

index.html

{% extends "base.html" %}

{% block title %}Test Dashboard{% endblock %}

{% block content %}
<div id="currentCount">{{ job_detail|length }}</div>
<br>
{% for line in job_detail %}
<div id="{{ line.id }}">{{ line.job_number }}</div>
{% endfor %}
{% endblock %}

{% block javascript %}
<script>
const webSocketBridge = new channels.WebSocketBridge();
webSocketBridge.connect("ws:/development01:8000/ws/");
webSocketBridge.listen();
webSocketBridge.demultiplex('updatedb_results', function(data, stream) {
console.log(data);
});
</script>
{% endblock %}

routing.py

from channels import route_class
from dashboard.consumers import Demultiplexer

channel_routing = [
route_class(Demultiplexer, path="^/ws/"),
]

Can anyone tell me where I'm going wrong?

Thanks,

Dan

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