I have a question on how to implement a server and multiple clients with data communication.
They share the same dataset for each step. That is, a server gets the same step's data for each client. I have no idea how to sync all clients and communicate data file for each step.
Can you give me some hints or a basic idea? An example will be perfect.
Take a loot at these
Multi-threaded multi-client server in python
Client Server programming in python?
http://ilab.cs.byu.edu/python/select/echoserver.html
If you don't want to deal with details like socket and connection handling and you like high diving, you should look into Twisted
Here's a SO answer with a simple example of a server using Twisted
Related
I have server which must nofity some clients across gRPC connection.
Clients connect to server without timeout and wait for messages every time. Server will notify clients when new record was added to database.
How can I manage server for better performance with multithreading? May be should I use monitor and if record was added I would notify server side gRPC to retrieve data from database and send it to clients?
How do you think?
Thanks
We have some better plans for later in time, but today the best solution might be to implement something that presents the interface of concurrent.futures.Executor but that gives you better efficiency.
Send data read from GPiO to server, not only with WIFI, but also on mobile network outside anywhere. I dont have and dont want to deal with setting a public address for RPi2, so this is why I need RPi2 to be client, sending data thru websockets to server on public address. It could be node.js, python, PHP client - server, as long as it is without of the need for a browser at the client side RPi2. Any suggestions ? Thank you.
Additionally, can you please explain how would "server side node.js client" work ?
An (incomplete) list of libraries with websocket support
For Python, you could look at:
Tornado Web
Twisted Matrix
Autobahn
Crossbar.io
For node.js you could look at:
socket.io
web-socket-js
Also, you should consider editing your question. Just ask one at a time. Your second question you should research yourself, a little googling would get a link or two to a nice article explaining what you would like to know.
I need to have a tcp socket client connected to a server to send data and receive.
But this socket must be always on and i cannot open another socket.
I have always some data to send over the time and then later process the answer to the data sent previously.
If i could open many sockets, i think it was more easy. But in my case i have to send everything on the same socket asynchronously.
So the question is, what do you recommend to use within the Python ecosystem? (twisted, tornado, etc)
Should i consider node.js or another option?
I highly recommend Twisted for this:
It comes with out-of-the-box support for many TCP protocols.
It is easy to maintain a single connection, there is a ReconnectingClientFactory that will deal with disconnections and use exponential backoff, and LoopingCall makes it easy to implement a heartbeat.
Stateful protocols are also easy to implement and intermingle with complex business logic.
It's fun.
I have a service that is exactly like the one you mention (single login, stays on all the time, processes data). It's been on for months working like a champ.
Twisted is possibly hard to get your head around, but the tutorials here are a great start. Knowing Twisted will get you far in the long run!
"i have to send everything on the same socket asynchronously"
Add your data to a queue, have a separate thread taking items out of the queue and sending via socket.send()
I have a big problem, and I am having a hard time solving it. I have a custom made game controller, which outputs some data from it's sensors via serial communication and is connected to PC via serial port. I do the callculation of the current controller position in a Matlab script. I am building a web application that will display the data (position) of the device in a web browser, but can't seem to work out, how to connect my device to the browser. Matlab script sends all the position data to a UDP port with a sampling fequency of 100HZ (100 samples per second). I need to make a persistent connection between a web browser and my matlab script so I will be able to display the data. I am thinking about using web sockets API. but it does not "speak" UDP. So my idea was to somehow read the data with from UDP with a custom Python server and then create a websocket on that Python server and send data received via UDP port to web browser. Oh, and it would be nice if I could communicate in both directions. Will this work? Any ideas on how to do it? How is this usually done, I mean how can one connect let's say some temperature sensor to web browser to display data in real time?
Any answer will be gladly appreciated.
Thanks,
Leon
Note that although the WebSockets protocol is built on TCP sockets, the WebSockets protocol is not raw TCP sockets. A WebSockets connection has an HTTP friendly handshake (with some CORS functionality built-in). WebSockets are also message based (rather than streaming like TCP) so each message has a couple of bytes of framing headers.
You might look at websockify (disclaimer: I made websockify). Websockify is a python server that bridges/proxies between WebSockets and plain TCP sockets. I don't think it would be particularly difficult to adapt it to handle UDP sockets on the backend.
WebSockify (designed to be used together with the included include/websock.js front-end library) supports binary data even over the older Hixie versions of the protocol. This allows it to work with iOS (iPhone,iPad) devices which still only support the older version of the protocol.
I am developing a testbed for cloud computing environment. I want to establish multiple client connection to a server. What I want is that, server first of all send a data to all the clients specifying sending_interval and then all the clients will keep on sending their data with a time gap of that time_interval (as specified by the server). Please help me out, how can I do the same using python socket program. (i.e. I want multiple client to single server connectivity and also client sending data with the time gap specified by server). Will be great-full if anyone can help me. Thanks in advance.
This problem is easily solved by the ZeroMQ socket library. It is production stable. It allows you to define publisher-subscriber relationships, where a publishing process will publish data on a port regardless of how many (0 to infinite) listening processes there are. They call this the PUB-SUB model; it's in their docs (link below).
It sounds like you want to set up a bunch of clients that are all publishers. They can subscribe to a controlling channel, which which will send updates to their configuration (how often to write). They also act as publishers, pushing out their own data at an interval specified by default/config channel/socket.
Then, you have one or more listening processes that listen to all the clients' published messages. Perhaps you could even have two listening processes, one for backup or DR, or whatever.
We're using ZeroMQ and loving the simplicity it gives; there's no connection errors because the publisher doesn't care if anyone is listening, and the subscriber can start before the publisher and if there's nothing there to listen to, it can just loop around and wait until there is.
Bindings are available in ALL languages (it's freaky). The Python binding isn't pure-python, it does require a C compiler, but is frighteningly fast, and the pub/sub example is a cut/paste, 'golly, it works!' experience.
Link: http://zeromq.org
There are MANY other methods available with this library, including message queues, etc. They have relatively complete documentation, too.
Multi-Client and Single server Socket programming can be achieved by Multithreading in Socket Programming. I have implemented both the method:
Single Client and Single Server
Multiclient and Single Server
In my GitHub Repo Link: https://github.com/shauryauppal/Socket-Programming-Python
What is Multi-threading Socket Programming?
Multithreading is a process of executing multiple threads simultaneously in a single process.
To understand well you can visit Link: https://www.geeksforgeeks.org/socket-programming-multi-threading-python/, written by me.