I building a Socket.io App.
This is the Node.Js Server Code, running in AWS instance:
var server = require('http').createServer();
var io = require('socket.io')(server);
io.on('connection', function(client){
io.sockets.emit("welcome"); //This is received by everyone
client.on('message', function(msg){
console.log("message arrived"); //This is executed
io.sockets.emit("welcome"); //This is not received by Python Client
});
});
server.listen(8090);
I have different clients, running on web page with Javascript and one Python client running in my local computer.
This is the Python client:
from socketIO_client import SocketIO
socket_url = "http://xxxxxxxxxxxxxx.eu-central- 1.compute.amazonaws.com"
socketIO = SocketIO(socket_url, 8090, verify=False)
def welcome():
print('welcome received')
socketIO.on('welcome', welcome)
socketIO.wait(seconds=1)
while True:
pass
The problem:
Python client receives the "welcome" only when the socket start, but when other clients send the "message" to the server, and it re-transmit the "welcome" to all clients, the Python client does not receive it. The others clients receive this specific "welcome", so the problem is the Python client.
I am using https://pypi.python.org/pypi/socketIO-client for the Python client. And Socket.io npm version 1.7.2 due to this issue
https://github.com/invisibleroads/socketIO-client/issues/159
I found the problem.
It was the line:
socketIO.wait(seconds=1)
SocketIO was responding only for 1 second, so everything that arrive after 1 second is ignored.
socketIO.wait()
Solve the problem
Related
Im having an issue that's related to the python implementation of the socket.io module.
Basically the official javascript documentation of socket.io describes a pre connection authentication handshake that can be send via the client directly when connecting to the server
client.js
var io = require('socket.io-client');
var socket = io.connect('http://localhost:80', { auth: "sample token" });
my issue is that the socket.io documentation for python doesn't describe anything like it
Does anyone have an idea how to do this using the socket.io python module ?
I am trying to test a Mosquitto MQTT server. My plan is to hopefully get it to ingest some notifications from our monitoring system in my work IT dept. Seems perfect for the task. I was able to install Mosquitto on a Ubuntu 20.04 server, and testing with the mosquitto_sub and mosquitto_pub clients worked right away (see attached screenshot). I also was able to Google around and set up some Python script using paho mqtt module for subscribe and publish. I set up the subscribe script as a service and it runs fine. I can receive published messages from both mosquitto_pub and the "publish" Python script...
Now where the issues come up is when I try publishing to the Mosquitto server from a remote computer within my office. For the life of me I cannot determine what the issue is. :(
I am able to telnet to the Mosquitto server on port 1883 so it does not seem to be a firewall issue on the Mosquitto server... Whenever I try to use the publish Python script from the remote computer, it executes but it does not work -- no messages are received at the subscriber running on the server. One odd thing is that the "on_connect" portion on the script does not work when the script is run on the remote computer; no "Connected to MQTT Broker!" message is printed when the script is run remotely. (it does work when it's run locally on the Mosquitto server).
I am attaching a screenshot of my /etc/mosquitto/conf.d/default.conf file. I have tried all sorts of combinations on the config and each time things work when run on the server itself but not remotely. I tried putting the IP address for the server on the config as "listener 1883 10.x.x.x". (Note for this post using "10.x.x.x" instead of my real IP address.) The last thing I tried was putting the adapter name, and still does not work. As you can see I have also defined authentication (usernames, passwords) for a pubuser and subuser. The account info does work with the mosquitto_sub and mosquitto_pub clients, and when used in Python scripts (when script are run on Mosquitto server) so I don't think it's an account info issue. All signs are pointing to either some misconfiguration I have in Mosquitto, or some firewall policy in my work location. Please help!
Please share any tips or possible fixes for me. I might be doing something wrong in my config; please do let me know if you see something amiss. I am a newbie with Mosquitto and MQTT but would love for it to work, kind of ruins the point if I cannot publish to the server form a remote computer though :)..
Below is example Python code I am using on the remote computer to publish (works run locally on the Mosquitto server). I redacted the IP address of the server with 10.x.x.x).
When I run the script from the remote computer I just get "Failed to send message to topic python/mqtt".
:
import random
import time
from paho.mqtt import client as mqtt_client
broker = '10.x.x.x'
port = 1883
topic = "python/mqtt"
# generate client ID with pub prefix randomly
#client_id = f'python-mqtt-{random.randint(0, 1000)}'
#Set the static client id
client_id = 'python-mqtt01'
username = 'pubuser'
password = 'something'
def connect_mqtt():
def on_connect(client, userdata, flags, rc):
if rc == 0:
print("Connected to MQTT Broker!")
else:
print("Failed to connect, return code %d\n", rc)
client = mqtt_client.Client(client_id)
client.username_pw_set(username, password)
client.on_connect = on_connect
client.connect(broker, port)
return client
def publish(client):
msg_count = 0
while True:
time.sleep(1)
msg = f"messages: {msg_count}"
result = client.publish(topic, msg)
# result: [0, 1]
status = result[0]
if status == 0:
print(f"Send `{msg}` to topic `{topic}`")
else:
print(f"Failed to send message to topic {topic}")
msg_count += 1
def run():
client = connect_mqtt()
client.loop_start()
publish(client)
if __name__ == '__main__':
run()
Thanks for reading! Hopefully someone out there has encountered the same issue and fixed it!
P.S. - forgot to mention I also disabled the firewall on the Ubuntu server until I get things working (ufw disable).
Example of my default.cfg (before) removing adapter and adding log_type all:
listener 1883
allow_anonymous false
bind_interface ens33
I am quite new to MQTT and brokers, but I am having an issue with VerneMQ not sending offline messages to clients. Here is my setup. I have a backend written in Python which is using the Paho Eclipse MQTT library's single() method to send messages to a connected client. The client, a virtual machine on my development station, has a client which is written in go-lang, using paho.mqtt.golang to connect to the broker and subscribe.
The call to single() on the backend looks like this:
def send_message(device_id, payload):
token = get_jwt('my_token').decode()
mqtt.single(
f'commands/{device_id}',
payload=payload,
qos=2,
hostname=MESSAGING_HOST,
port=8080,
client_id='client_id',
auth={'username': 'username', 'password': f'Bearer {token}'},
transport='websockets'
)
On the client, the session is established with the following options:
func startListenerRun(cmd *cobra.Command, args []string) {
//mqtt.DEBUG = log.New(os.Stdout, "", 0)
mqtt.ERROR = log.New(os.Stdout, "", 0)
opts := mqtt.NewClientOptions().AddBroker(utils.GetMessagingHost()).SetClientID(utils.GetClientId())
opts.SetKeepAlive(20 * time.Second)
opts.SetDefaultPublishHandler(f)
opts.SetPingTimeout(5 * time.Second)
opts.SetCredentialsProvider(credentialsProvider)
opts.SetConnectRetry(false)
opts.SetAutoReconnect(true)
opts.willQos=2
opts.SetCleanSession(false)
I am not showing all the code, but hopefully enough to illustrate how the session is being set up.
I am running VerneMQ as a docker container. We are using the following environment variables to change configuration defaults in the Dockerfile:
ENV DOCKER_VERNEMQ_PLUGINS.vmq_diversity on
ENV DOCKER_VERNEMQ_VMQ_DIVERSITY.myscript1.file /etc/vernemq/authentication.lua
ENV DOCKER_VERNEMQ_VMQ_ACL.acl_file /etc/vernemq/vmq.acl
ENV DOCKER_VERNEMQ_PLUGINS.vmq_acl on
ENV DOCKER_VERNEMQ_RETRY_INTERVAL=3000
As long as the client has an active connection to the broker, the server's published messages arrive seamlessly. However, if I manually close the client's connection to the broker, and then publish a message on the backend to that client, when the client's connection reopens, the message is not resent by the broker. As I said, I am new to MQTT, so I may need to configure additional options, but so far I've yet to determine which. Can anyone shed any light on what might be happening on my setup that would cause offline messages to not be sent? Thanks for any information.
As thrashed out in the comments
Messages will only be queued for an offline client that has subscribed at greater than QOS 0
More details can be found here
You need to make QOS to 1 or 2 depending on your requirement and also you can use --retain flag which is quite useful. retain flag will make sure that last message will be delivered irrespective of any failure. You can know the last status of device. Check this http://www.steves-internet-guide.com/mqtt-retained-messages-example/
I'm trying to make JavaScript client to a Python websocket server through an Apache2 proxy.
The client is dead simple:
const socket = io({
transports: ['websocket']
});
I have a NodeJS websocket server and a working Apache2 reverse proxy setup.
Now I want to replace the NodeJS server with a Python server - but none of the example implementations from socket.io works. With each of the my client reports an "error 400" when setting up the websocket connection.
The Python server examples come from here:
https://github.com/miguelgrinberg/python-socketio/tree/master/examples/server
Error 400 stands for "Bad Request" - but I know that my requests are fine because my NodeJS server understands them.
When not running behind a proxy then all Python examples work fine.
What could be the problem?
I found the solution - all the Python socket.io server examples that I refered to are not configured to run behind a reverse proxy. The reason is, that the socket.io server is managing a list of allowed request origins and the automatic list creation is failing in the reverse proxy situation.
This function creates the automatic list of allowed origins (engineio/asyncio_server.py):
def _cors_allowed_origins(self, environ):
default_origins = []
if 'wsgi.url_scheme' in environ and 'HTTP_HOST' in environ:
default_origins.append('{scheme}://{host}'.format(
scheme=environ['wsgi.url_scheme'], host=environ['HTTP_HOST']))
if 'HTTP_X_FORWARDED_HOST' in environ:
scheme = environ.get(
'HTTP_X_FORWARDED_PROTO',
environ['wsgi.url_scheme']).split(',')[0].strip()
default_origins.append('{scheme}://{host}'.format(
scheme=scheme, host=environ['HTTP_X_FORWARDED_HOST'].split(
',')[0].strip()))
As you can see, it only adds URLs with {scheme} as a protocol. When behind a reverse proxy, {scheme} will always be "http". So if the initial request was HTTPS based, it will not be in the list of allowed origins.
The solution to this problem is very simple: when creating the socket.io server, you have to either tell him to allow all origins or specify your origin:
import socketio
sio = socketio.AsyncServer(cors_allowed_origins="*") # allow all
# or
sio = socketio.AsyncServer(cors_allowed_origins="https://example.com") # allow specific
I am trying to create and node.js api to which users can subscribe to get event notifications?
I created the below API and was able to call the API using python ,however its not clear to me how can folks subscribe to it?
How can folks subscribe to this API to get notification of New root build released?what do I need to change?
node.js API
app.get("/api/root_event_notification", (req, res, next) => {
console.log(req.query.params)
var events = require('events');
var eventEmitter = new events.EventEmitter();
//Create an event handler:
var myEventHandler = function () {
console.log('new_root_announced!');
res.status(200).json({
message: "New root build released!",
posts: req.query.params
});
}
import requests
python call
input_json = {'BATS':'678910','root_version':'12A12'}
url = 'http://localhost:3000/api/root_event_notification?params=%s'%input_json
response = requests.get(url)
print response.text
OUTPUT:-
{"message":"New root build released!","posts":"{'root_version': '12A12', 'BATS': '678910'}"}
You can't just postpone sending an http response for an arbitrary amount of time. Both client and server (and sometimes the hosting provider's infrastructure) will timeout the http request after some number of minutes. There are various tricks to try to keep the http connection alive, but all have limitations.
Using web technologies, the usual options for get clients getting updated server data:
http polling (client regularly polls the server). There's also a long polling adaptation version of this that attempts to improve efficiency a bit.
Websocket. Clients makes a websocket connection to the server which is a lasting, persistent connection. Then either client or server can send data/events of this connection at any time, allowing the server to efficiently send notifications to the client at any time.
Server Sent Events (SSE). This is a newer http technology that allows one-way notification from server to client using some modified http technology.
Since a server cannot typically connect directly to a client due to firewall and public IP address issues, the usual mechanism for a server to notify a client is to use either a persistent webSocket connection from client to server over which either side can then send webSocket packets or use the newer SSE (server sent events) which allows some server events to be sent to a client over a long lasting connection.
The client can also "poll" the server repeatedly, but this is not really an event notification system (and not particularly efficient or timely) as much as it is some state that the client can check.