I have created server daemon, that produces some data, like messages and so. But, what im interested in - client monitoring. For example i have web page, and i need to establish persistent Tcp connection to server and show all incoming data into textbox. I know it can be done with flash, but im searching for JS implementation.
Is it possible and what`s the best practices ?
What you're asking for is known as Comet. Plenty of server software and client libraries exist - see the linked Wikipedia page.
WebSockets is designed to solve this problem.
Related
I've got a web application that's running Js on client side and c# on server side - What would be the best way for them to communicate over the internet and how would I pull that off - would really appreciate some resources, I've been looking around for a bit now and couldn't find anything.
There wont only be credentials from forms that will be passed through, there will be other data coming from the server time to time as well
The best answer is WebSocket. I believe that there is good support for this in c#, and I know for myself that it's pretty easy to set up in JavaScript. You can use "ws" or a secure connection with "wss".
The one thing I would warn you about is with "credentials" and sensitive information in JavaScript. On the client side, you basically have no control over preventing sensitive information from leaking. Web pages can be altered and inspected by the client. So be careful about what your server sends to your client.
I have a c# tcp server, I want to connect to the server via a html client page.
The problem: There is no simple way to create TCP sockets in Javascript on a browser side. Although solutions like Websockets allow to create something that resemble sockets, you can use them to connect only to servers that support Websockets. Not to any random servers that know nothing about HTTP.
so is there a solution to connect to my srver.
No. There just isn't. The browser is a tightly locked down environment. The only socket connection that you can open from JavaScript is WebSocket. Since it's your server, adding WebSocket support shouldn't be too complicated, and there are WebSocket libraries available for C#.
Maybe someone else will have an idea for you, but...
The best solution I can think of is for your server to support websockets.
The situation you described - along with connectivity issues for traffic passing through proxies and routers - is one of the reasons Websockets were introduced in the first place.
Bare in mind that Websockets can send and receive binary data. It's just that javascript make it more comfortable to write text based messages.
Also, many NAT routers, Proxies and firewalls will block raw TCP/IP communication while allowing Http communication to pass through. This is why you have a better chance at connection establishment and retention when implementing the Websocket protocol.
I have built a website with PHP + Apache + JS + HTML 5. Now there is a point where I have to tell the user every second if the server is connected and ready to receive data and/or internet connection is lost/available or whatever else which can tell the user to not to send data to server because of unavailability of Server or internet connection.
For this purpose I can either move to Long Polling with Ajax and keep pinging my server every second but surely this will cause alot of network overhead on my Apache Server where my clients are about tens of thousands live at a time so keep pinging the server is not a good option. Therefore, I decided to use WebSockets.
I have been googling for about 2 days but yet could not find enough good article to answer my 3 basic questions regarding WebSocket and Apache + PHP.
1) If once the WebSocket connection is made with server, then does it remain active like Long Polling with Server or what is the mechanism behind it? I mean how does WebSocket maintain its relation with server does it keep polling with server and hence there is always a connection between Client and Server?
2) If your answer to above question is yes then what network/IO overhead would be on server side if I use websockets because there is a continuous connection between Client and Server. And imagine if there are hundreds of thousands of clients online at a time what load will it create on Server Network or IO?
3) What is the Best approach to use WebSockets when using Apache + PHP on server? Any good article on this where I can study how to communicate with Apache Server using WebSockets? I found this question, but it doesn't answer well Using WebSocket on Apache server. In this question, it limits the experts to not to include any answer which has sysadmin tools, while I am asking for it if any required.
I have a VPS Server so tunning and installing some tools isn't a problem.
Any help would be highly appreciated. Thanks with Regards.
1) If once the WebSocket connection is made with server, then does it remain active like Long Polling with Server or what is the mechanism behind it? I mean how does WebSocket maintain its relation with server does it keep polling with server and hence there is always a connection between Client and Server?
Yes, it remains active and there is always a connection between Client and Server. However, the client needs to maintain the connection and on connection exceptions. In this case, it is your javascript code.
2) If your answer to above question is yes then what network/IO overhead would be on server side if I use websockets because there is a continuous connection between Client and Server. And imagine if there are hundreds of thousands of clients online at a time what load will it create on Server Network or IO?
WebSocket connections are handled on TCP/IP level and by definition, they are not resource consuming operations when there is no data going through the TCP tunnel. So rather than worrying about your CPU and memory conception, you need to worry about the limit on the number of connections. Consider using a load balancer for your socket connections and utilize multiple servers if you are expecting more than 10000 concurrent connections.
3) What is the Best approach to use WebSockets when using Apache + PHP on server? Any good article on this where I can study how to communicate with Apache Server using WebSockets? I found this question, but it doesn't answer well Using WebSocket on Apache server. In this question, it limits the experts to not to include any answer which has sysadmin tools, while I am asking for it if any required.
For such a use case of yours - getting the status of the server, I would suggest using a message broker rather than load this simple operation to Apache.
Please consider looking at mosquitto, hivemq or rabbitmq
All of them are supporting WebSockets and all of them have their pros and cons. Do the small proof of concepts over them and choose what is best for you.
I am interested to know if anyone has built a javascript websocket listener for a browser. Basically the server side of a websocket that runs in a client. This would allow messages to be sent to the client directly. Why? Because instead of having a Node.js, python, java, etc, server process sitting on or near the client/browser, I can just use a thread in the browser as a listening server thread. I don't think that any browsers support this currently.
I've run across answers like this: https://news.ycombinator.com/item?id=2316132
Just curious if anyone has done this. I believe that the current Websockets spec does not support listeners on the browser. It would make the deployment of various peer-to-peer applications a bit easier to deploy.
WebRTC allows for peer-to-peer connections to be made between browsers.
You would still need a server in order for individual users to discover each other but then they could connect directly to each other rather than having to pass all their traffic via a central server.
The idea.
You can use a simple echo server written in any language. Your script can send the data to the server then get it back, handle it on the same page with different functions/classes emulating the real server.
An example: http://www.websocket.org/echo.html
Then, you can think about different formats of packets to/from server to diffirentiate them inside one script.
I recently asked one question :- Handle Web Server with multiple clients
I have gone through the basic techniques to implement comet server like streamhub,Maven/Jetty etc.
I have following questions for that :
After that I found the issues like in case of Maven/Jetty internet
connection is required for downloading certain files from net.So it
it possible to implement it if no internet connection is there on
machine where the web server is hosted ?
Also I want the open source tools/technologies to achieve the thing
mentioned in the above question. and I think stream hub is not a
open source free version. Please help if you know any tool which is
free/open source to use.
Currently the web application is running on apache web server. so if
I use comet server what changes I need to do in that ??
Please help...
Thanks in advance...
For comet, pick a server which can handle many open connections. For a chat app I implemented which currently handles 10k open connections, I used Mochiweb. You might want to give that a look.
Going along the Mochiweb path, I will also recommend Erlang for implementing you server. It will be a small piece of code. Basically, you will listen on a path and hold the connection open till you have some data to respond with or timeout.
On the client side, you would write a simple JS function which will make an AJAX call and handle response timeout and data responses as and when they come. Nothing too different here. However, you may need JSONP instead (crossdomain/subdomain because of different servers for web and long poll), so ensure that your LongPoll server replies accordingly.