I've to write an Ajax chat web application in ASP.NET for a friend, and I've a question: if client1 sends a message to client2, how should the application send the message to client2? Is there a better way than sending requests to the server, "asking" if there are new messages? Is it possible to directly send the message to the client?
Best thing you can do is use a Persistent HTTP Connection. The way google does with Google Talk on their GMAIL website.
Remember that HTTP is a stateless protocol and that each transaction is made from the client to the server.
The server can use sessions to determine if this client is "known" but as for sending information back to the client using plain old HTTP I think that is impossible (I mean from a server initiated connection, not a response to the client)
You would need to use Javascript to poll the server for information.
If you want it the other way around, you could possibly use Java or Flash but then you also need to think about NAT tunneling, proxy servers and any other weird setups that the clients could be using.
No. I don't think the server can send message to client's browser.
Here is how I implement chat application:
client1 post message via Ajax to server
server save it to repository (I'm using singleton object for this case)
client2 get the message from repository
mark the message as read
I will save chat logs to database once the chat session closed or expired.
Related
Recently we deployed a Blazor application to one of our clients. When their internal team did a WARP test, we got a finding "ClearText transmission of Sensitive Information". When we analyzed it we found that the Blazor heartbeat is sending values typed in every input field to the server via "DispatchBrowserEvent". Given below is a screenshot of the same.
DispatchBrowserEvent
I need a solution to either
Encrypt the value being sent in the DispatchBrowserEvent or
To Stop the transmission of the values until its manually posted.
Blazor Server uses SignalR as the communication mechanism so data is sent back and forth to the server. It should be on an encrypted channel using SSL/TLS, so I assume your site has SSL enabled?
Login credentials have to be sent from the browser to the server in a POST to validate them. This is the same for all web applications. You just have to ensure that the requests are done over SSL so that only the client and the server can read them. This is not a security issue if this the case.
Secondly, the preferred mechanism SignalR/Blazor-Server uses is WebSockets. If your app was using a WebSocket connection you would not see the traffic you are seeing - this is because SignalR will fall back down to alternative methods if WebSockets are not available.
You should check your server to see if WebSockets is enabled - I suspect that is the cause.
I'm using SignalR and a web farm in IIS, currently with 3 servers and requests are load balanced via ARR.
There are certain external events that happen which I want to be processed by the server to which the client is connected. So I want to track which of the 3 servers the client is currently connected.
I thought that I could do this using OnConnected and within that method store the MachineName against the ConnectionID in redis.
The problem is that OnConnected seems to get called an a different server to the one that the client is connected to.
Upon investigating, it seems that there are three calls, one to /negiotate one to /connect and one to /start. The /connect seems to be the websocket connection that is kept up for the duration, the others are just transient.
These three connections can happen on different servers, and it seems that the websocket connection can be to server A (so that's the server that the client's SignalR connection is going to), but the OnConnected gets fired on server B.
I was wondering if I'm overlooking something that will let me see which server the SignalR connection is actually connected to?
Thanks,
Will
If you are going to use a web farm, then you need to implement a backplane to track all of the messaging.
https://learn.microsoft.com/en-us/aspnet/signalr/overview/performance/scaleout-in-signalr
Without a proper backplane implementation its impossible to do what you want to do.
I believe that is something you would have to save. Assuming you are using a database for mapping users, you could have an additional field such as "LoggedInOn" and store the server host name or other identifier.
However, other than some aspect of troubleshooting your are looking to do, proper send/receive of messages should cross the backplane to all servers. This way no matter which server they are connected to, messages are received.
If you have external events as you say, once they complete and a message is ready to be sent back to a client, the backplane should push that to all servers.
If that's not happening I would review the docs as Kelso Sharp stated.
Help needed please
What's is the best WebSocket client library for a .net 4.5 on windows web application hosted on windows 2008 servers to connect to a remote server web socket.
The scenario is: our web application will use a web socket to connect to a server WebSocket on a third party infrastructure. Our client WebSocket will connect and send some commands and read the responses where we can identify the information needed. So there is no interaction from the user or browser its just in the code. e.g. user clicks a button and we go and get some data, and give a message dependant on the response.
so for example our client will connect to the third party socket and pass the users car registration number and send a tell me the car details and the server socket will return the data like: make, model, year etc... so we can then display that to the user.
Has anyone used this library with some good success? http://www.nuget.org/packages/WebSocket4Net
I'm hoping someone here can provide the best approach for doing this with some tried and tested solutions. I have been thinking about a web API that handles all the socket stuff in our client so i can call it and let it handle the close connection etc.
Can anyone tell me how can we send server to server message with signalR?
I am creating chat application for that I used sub domain concept as there was problem in opening multiple concurrent connections with signalr. But using subdomain concept, chat is not implemented properly as it does not send message to connection opened from other subdomain. Can any one suggest me solution that how can we send messages to and from server in signalR?
I have already tried to implement centalized approach to store and use the connectionID but not worked.
We have a requirement wherein the server needs to push the data to various clients. So we went ahead with SSE (Server-Sent events). I went through the documentation but am still not clear with the concept. I have following queries :
Scenario 1. Suppose there are 10 clients. So all the 10 clients will send the initial request to server. 10 connections are established. When the data enters the server, a message is pushed from server to client.
Query 1 : Will the server maintain the IP address of all the client? If yes is there an API to check it?
Query 2: What will happen if all the 10 client windows are closed? Will the server abort all connections after a period of time?
Query 3: What will happen if the Server is unable to send messages to client due to unavailability of client like machine shutdown. Will the server abort all connections after a period of time for those client for whom they are unable to send the message?
Please clarify?
This depends on how you implement the server.
If using PHP, as an Apache module, then each SSE connection creates a new PHP instance running in memory. Each "server" is only serving one client at a time. Q1: yes, but not your problem: you just echo messages to stdout. Q2/Q3: If the client closes the connection, for any reason, the PHP process will shutdown when it detects this.
If you are using a multi-threaded server, e.g. using http in node.js. Q1: the client IP is part of the socket abstraction, and you just send messages to the response object. Q2/Q3: as each client connection closes the socket, the request process that was handling it will end. Once all 10 have closed your server will still be running, but not sending data to any clients.
One key idea to realize with SSE is that each client is a dedicated socket. It is not a broadcast protocol, where you push out one message and all clients get exactly the same message. Instead, you have to send the data to each client, individually. But that also means you are free to send customized data to each client.