I want to make a server using python, and the auto discover it using a web aplication.
I know i can make a python->python discovery using How to make a server discoverable to LAN clients from this thread. But i can't find a way to make the javascript discover that server.
It would be great if I could use the same connection, or at least the same port to make a socket server where i can send commands back and forth.
Any ideas?
Related
I have PHP on the server side, and HTML and javascript on the client side.
I am making an app where a stakeholder types a message that is broadcasted to multiple recievers of a group in real time.
I did some research on google and I understand I need to use WebSockets or Comet for real time push notifications. Is WebSocket or Comet mandatory for sending mass notifications to users?
Is my understanding correct? Any references to start with?
If the client is a browser, then the ONLY two ways a standard browser can connect to a server is via an Ajax (e.g. http) request or a webSocket connection. So, if you want a client to get notified of something from the outside world it has to use one of those two mechanisms.
HTTP requests are transitory. The client makes a request of a server, the server responds. HTTP requests are perfect for the client requesting information from the server. They are not very good at the server sending information to the client because normally the client is not connected. There are hacks and work-arounds where the client "polls" the server on some interval and maybe even the server uses longer running requests to try to simulate a "push" type system, but they are sub-optimal hacks at best.
webSockets are continuous connections. The client connects and the connection remains in place for as long as both sides want. This allows either side the ability to send a message to the other side whenever they want. That means the server can "push" data to the client whenever it wants. webSockets are efficient for push connections and are recommended (this is one of the main things they were designed for).
Comet is a library that was originally built for using HTTP to try to "hack" or "simulate" push before webSockets were invented and then before they were widely supported. I can think of no reason why one would want to use Comet instead of a webSocket unless you had such an old browser that webSocket was not supported.
So, if you are trying to do "realtime server push" to a browser, then you must have a continuously connected socket from the client which means webSocket (or something built on top of webSocket like socket.io).
For phone apps where you have access to the phone SDK, you can use the "push" system built into the OS to push some messages from server to client. This isn't quite the same as the two way webSocket channel, but since you asked about "push notifications", the OS push services available in both Android and IOS could also be an option for pushing notifications from server to client. Here's info on iOS notifications and Google Cloud Messaging
As of 2016, one can also use Server-sent events in all modern browsers except Microsoft browsers (not supported yet in Edge or IE) to push data from server to client. Here's a browser compatibility table. Server-sent events use a long lasting HTTP connection, a special MIME type and a supporting client in order to be able to send events from server to client at any time. Unlike webSockets, server-sent events are one way only (from server to client). A client would then use a traditional Ajax call in order to be able to send data to a server (whereas with a webSocket data can be sent either way over the same webSocket connection).
Here's a good description of how server-sent events work: How do server-sent events actually work?
Is your client application a SPA? (Single Page application)?
It's very important because if not, you have to consider that everytime a client change page, connection with websocket server will be lost.
In this case you have to manage a queue because if stakeholder send a multicast request when one client is disconnected, client won't receive nothing.
Polling won't solve this situation too and it's an orrible solution because mobile clients (for example) with typical internet plan, will consume megabytes for unuseful "ping" traffic.
A real example of polling is a child in a car asking his dad every minute if they are arrived to a destination!
So, Is there a solution without using spa?
Yes, using a "shared storage" between stakeholder and clients, and using websocket only for "wake up" online clients saying: Hey there is something new, go to check!
Everytime a client open a page it will receive from backend also not-read notifications, taken from the storage.
When a stakeholder want to notify something, it will just store the notification message in the shared storage and send a "pulse" to notification server.
Notification server will forward the "pulse" to online clients (just in case someone is stuck reading a page).
If a "pulse" is lost because a client is changing page there is no problem because the client will bring notifications from the storage.
Every page will contain this logic:
Retrive number or unread notifications (server side)
Connect to the notification server after 5 seconds (javascript side).
Hope it helps.
I would suggest that using webSockets is a more efficient way compared to other options, why is this? Well when a client receives a notification that there's a change in the server there is no need to create an AJAX call to the server to get that change, it can be sent to the client with the same webSocket connection more easily than AJAX. This means efficient code and a faster running App!
Im looking form something to make socket connection between client, without pass through the server. Is there any node package to do this?. Server only send the other client socket, and the clients recieve and send data to each other..
Or, how can we make the implamantation. We need to make a server in client side, but we dont have node installed in the client..
The closest thing that currently exists in some form is not currently part of socket.io. It is called WebRTC and is implemented in Chrome currently. It allows the browser to connect with other browsers.
http://www.webrtc.org
The question is what kind of application is your client? If you are talking about ordinary webbrowsers you need to think about writing pluings (tough case).
If you are talking about clients you have more control then you should look at technique Puching the hole exploited by Skype or P2P apps.
http://it.slashdot.org/story/06/12/15/191205/how-skype-punches-holes-in-firewalls
In general the server is used for TCP sockets orchestration the acutall comunication go directly.
My goal is to have a gateway that sends SSH commands to a remote server from a webpage. There are a few browser based extensions, but I wasn't able to find any that were exposed via Javascript. Is there a way to accomplish this client-side without a proxy server in between?
I really don't even need async communications, I really just need a "fire and forget" bucket for SSH calls triggered from a webpage, hopefully without introducing another service somewhere.
You can check out Ajaxterm which is a web based terminal.
also check Orbited which is provides a JavaScript TCP socket API for real-time browser applications.
I hope that help you.
I'm really new to Node.js and have been wondering something. I'm trying to build a simple chat room application as a way of teaching myself how this all works.
The way I see it working is that I have a Node http server which serves the pages of my site (homepage, login, chat screen etc) and then I have a WS server which accepts short messages to relay to all connected users.
The thing is I can't work out if this is the correct way to approach this. Is it possible to authenticate users on the Node server and know that they have been authenticated on the WS server? Can they share some kind of session?
Any help is appeciated!
You don't mention what you're using to implement a WebSocket server, so I'll assume you're using socket.io. (If you're not, you should.)
You can use the socket.io handshake process to access the HTTP session state.
If you're using Express (once again, highly recommended), it's easy to tie the two together.
I write a browser game (php, javascript) and I do not know how to make a callback. necessary that the server itself
found a client and call the function (only had one)
Don't write a browsergame if you don't know the basics! Browsergames are way too complex to learn programming.
If you want to make the server notify a client about something you will need to keep a connection open (search keywords: COMET, long polling) as you cannot initiate connections from the server to clients.
For this I can suggest you using Firebase. It is a API that let you to add cloud Data management that your user clients do. You can use that communication to search for client.
If I understand your question, what you need is a socket. Since you're using PHP and Javascript, a WebSocket might be just what you're looking for. With WebSockets, the connection between the client and the server is persisted, so the server can just push data/messages to any or all of the clients connected to it at any point in time. Likewise, the any client connected to the server can push messages/data up to the server.
Here's a video that describes how it works a bit https://www.youtube.com/watch?v=oJxWhmt5m-o