I have a web server that listens for jQuery keyboard events and I would like to send a string of the status for a set of keys to another domain for processing.
What technology/language/protocol is able to do this on the server-side?
It must be able to send the updated status message upon immediate change as listened for by keyboard events like arrow keys.
This is not a standard server <-> client updating but rather client > server > another server.
Can a WebSocket be used to create a server-side connection to a remote location, not a client?
https://en.wikipedia.org/wiki/WebSockets
What technology/language/protocol is able to do this on the server-side?
Any modern server side language can do it, node.js, c#, python, php. Just write your condition and make the request from your server as client.
Can a WebSocket be used to create a server-side connection to a remote location, not a client?
Of course! Your server can be a client like any other device. NodeJS example
Related
I've developed a WebApp with Flask, where different threads check a status and, if something changes they send a new json to the client. Then the client, with the javascript, can update the html page.
Running the app in my LAN, different clients connect and everything work correctly.
If I run the app on a real server (such as AWS, by using "flask run --host=0.0.0.0" ), the clients can connect and show the web page, but they don't receive the json sent by the socket of the webapp.
In the WebApp, a thread sends the new json by calling a function that uses:
socketio.emit('update', {'number': new_json_FE}, namespace='/test')
While the javascript receives this message (and does something) in this way:
socket.on('update', function(msg) { ....}
It is very strange that the clients connected in the LAN receive correctly all the json sent by the socket, while in the web not: they only receive the json when they connect to, and I have to upload the page (they don't receive the socket messages).
Can you help me?
Thank you very much!
I would advise against the use of threads like you have described for this situation.
Instead I would probably create a new program, StatusUpdater, that is always running and which is connected via socket to your Flask-SocketIO backend. When it finds a change in status it sends w/e signal or payload it needs to, through a socket, to the Flask-Socketio server. The SocketIO server upon receipt of this StatusUpdater payload can then send a broadcast to all connected clients notifying the client of the update.
I'm developing an iOS app that requires realtime dual-way server/client messaging.
I'm trying to use WebSocket++ to develop a WebSocket server app on an AWS EC2. Have to use C++ because that's the only language I know on the server side.
The problem is I'm a fresh guy on server side development. I have 2 very basic questions:
1, Do I need have to setup an HTTP server like apache/nginx in order to get websocket running?
That is, can websocket app live independently alone?
2, I have now setup an nginx server in case it is a must have, is there any resource that I can refer to to make nginx & websocket work together well?
No, you don't need a Web server, a (reverse) Web proxy or anything to have your C++ WebSocket server talk to WebSocket clients.
Nginx (as HAproxy) supports reverse proxying WebSocket. This can make sense in certain situations, like you want to terminate TLS at the proxy and forward plain WebSocket to your backend server, or you want to load-balance incoming WebSocket connections to multiple backend nodes. However, as said, this isn't required.
No you don't, websocket and socket for an HTTP server are two diffent things.
HTTP server is for the HTTP protocol while there is not protocol defined for websocket, you have to define it yourself typically by the mean of sending/receiving Json message (a stream of character which each side (the server and the client) knows how to read/write).
The goal of websocket is to offer to javascript through HTML5 an easy, light and quick way to communicate through a socket, without websocket you have to do that with web services and in that case you need a http server.
With websocket you can create an html file leveraging html tag and javascript, javascript use client side of websocket to communicate with a C++/websocket server program, and you do not need even a web server, in this scenario you have a "desktop web app" ! (here web term is only because you use html tags)
Same question, same answer, no again ;-)
Good luck, and welcome in the wonderful world of asio !
As I mentioned in the title: I would like to know the difference between the web-service and the web-socket? when we used each one?
Thanks!
A web service is an HTTP server that responds to client SOAP/REST/JSON requests.
A web socket is a client-side API that allows a web browser to create a bidirectional communication link with a server without having to change/reload the current page. This is typically used for AJAX requests to dynamically update live content on the current page, or create chat sessions between clients, or implement custom protocols that run in the web browser.
Web services are based on HTTP protocol and use HTTP methods to relay data in a request and response paradigm. Thus the client will always be the one responsible for communicating with the server, requesting data and submitting data to the server i.e getting list of customers or products, adding products or customers to server.
In contrast, Web sockets allow bidirectional communication, meaning server can initiate communication as much as client can do the same. Typically you supply a host IP Address and port to the socket. Web sockets can be used to implement a chat application.
The key difference between Web sockets and Web services is that with web sockets you get bi-directional connection in which the server and client can continuously send messages back and forth while Web services are uni-directional connection concerned with supplying clients with resources
I have a client server based c++ application which communicates over network (with boost asio) and I am planning to distribute this client application to my customers. My problem is I don't know how to prevent connection request from other applications, that is how can I make sure that only my client application is able to connect to my server. I think there is no way to do this without making the connection, than what is the best way to verify that request is coming from my client?
You can use asio's builtin SSL ability. So, you generating sertificates for each server, and client sertificates. So you can check client sertificate on server at the moment of SSL handshake. As a bonus, your traffic will be encrypted and SSL-secure. Clients can check server is not a fake; server can check clients are authorized.
Yes you have to accept the connection in order to know if it's from your application or not.
You can use a three-way handshake at the connection step:
Client connects to the server The server is sending an specific
value (integer, strings or whatever) to the new client.
The client handles this value, compute a new one with it and sends
the new value to the server.
The server checks if the returned value is correct or not.
The client will have the same compute method as the server. The others applications will not be able to use your service if they returned a bad value.
I have a mini computer that does not support websockets that I would like to receive push notifications from a server.
The issue is that after the client connects to the server, the server responds and then closes the connection. This makes it so the client has to continually reconnect to the server to get new information.
Is there a way using Django to allow the connection to be left open and then have the server publish data to the client?
Django is primarily a request/response framework and as such does not have support for real duplex communication.
Socket.IO is the de facto library that makes websocket-like functionality cross-browser (IE5.5+), using real websockets as a transport if the browser allows it, falling back to HTTP long-polling or whatever else if it doesn't. For various options on integrating Socket.IO with Django, read this.