I'm currently using Alchemy Websockets as my WebSocket solution, however this is proving to be a pain as I've spent quite a number of hours trying to figure out why I can't get it up and going on my WebRole (both on Compute Emulator and cloudapp.net itself). It runs okay locally.
I'm aware of this question that was asked previously, and I've followed everything in the code and done everything suggested, so I can't get why I still can't connect to my WebSocket server. I've tried connecting using WebSocket.org's Echo Test as well as an Android client (leveraging on Autobahn). I'm quite sure it's not a client-side issue anymore considering that both ways don't work, but more of a server-side issue (what is stopping me from opening the WebSocket server on Azure?!).
In summary, what I've done so far:
Included TCP InputEndpoint 8080 in my Azure
Start the WebSocket server in either Global.asax or RoleEntryPoint with port 8080
Tried connecting using both Echo Test & Autobahn for Android
If it helps, I've previously tried SuperWebSocket Server. I understand that the creator Kerry Jiang has uploaded some Azure samples, but the Command Assembly baffles me and I don't want that kind of extra logic in my application (I just want something that I can plug and play), so I decided to ditch that altogether.
Both Alchemy Websockets and SuperWebSocket Server work perfectly fine locally, but when it's on Azure (either emulator on uploaded on cloudapp.net) I can't seem to connect at all. Any guidance please...?
When using WebSocket with cloud-hosted VMs, a number of things can go wrong:
The cloud service might have firewalls in place that block any (non-standard) ports by default. On Amazon EC2, you can configure open (unblocked) inbound ports via AWS management console and the respective configuration of the "security group" that applies to the EC2 instance your WS server is running on.
Even if you use a standard Web port (like 80) and this port is open in the firewall, there might be a proxy, load-balancer or other so-called intemediary in place that is not WebSocket aware.
When running over non-local networks, there are all kinds of intermediaries that might interfere. For example, mobile networkwork providers have intermediaries that are too stupid for WebSocket (which uses the HTTP standard Upgrade mechanism .. it is standard .. but there is a lot of broken stuff out there).
To work around for 2. and 3. (and also in general), you probably want to run WebSocket over TLS (secure WebSocket .. WSS) in production. Running over TLS, and terminating the TLS connection at your server, no intermediary can interfere (there are exceptions even here .. so called MITM HTTPS proxies that unwrap the TLS .. but that only on some corporate networks and relies on the proxy being able to dynamically installing certificates in the user's browser).
To make a robust WSS connection, you MUST make sure the server certificate used is accepted by browsers without any problems. If it is self-signed e.g., a browser would normally not accept, but ask the user if he nevertheless wants to accept. With WS, the browser will not render such dialogs, because WS is a so called "subresource". Hence: make sure your cert is 100% ok.
With 5. being done, WebSocket (WSS then), will work (almost) all the time. Mobile, enterprise, public internet.
Related
I have a self-hosted C# Windows Service written with VS2015 that includes SignalR and uses version 2.2.2 and jquery 3.2.1. It works fine for all the systems that use a "real" (addressable) IP address. But the computers that are behind a NAT cannot. They get a "SignalR: Error loading hubs. Ensure your hubs reference is correct, e.g. " error. If you use the URL http://servername/signal/hubs", you get a "Server took too long to respond" error. (clients with real IP's see the source).
Windows Firewall is disabled on the clients. However, the SignalR service is running on 80 and 443 so I wouldn't think that would be a problem. Anyway, I'm so confused at this point, I don't even know what code to post.
What can I check, do, post to figure out why this is not working for NAT'd clients?
EDIT: I had some other people test this and found two of us that use U-Verse had the connection problem. However, the people in the main office who are on the corporate NAT were connecting. So maybe this is something in the U-Verse router/firewall that's stopping the connection. But why would it block ports 80 and 443? Does SignalR do any out of the ordinary on a connection?
EDIT #2: I ran Wireshark on the server. It receives the request from the NAT'd client but keeps retrying to send the response to port 80. I'm not really good at understanding Wireshark or what to look for. Obviously, something is not working properly.
This was quite stupid on my part. I was using a server solely for SignalR that did not have IIS installed... and apparently you need to do that in order for ports 80 and 443 to be open in the firewall. The firewalls on all 18 servers are set to allow access from any of my domain's IP addresses. When using NAT, it uses a completely different IP and therefore was stopped. I opened 80/443 on the SignalR server and all is well... D'oh!
I have an multi layered application that I have developed. I communicate with the windows service using http with ServiceStack (AppHostHttpListenerBase). While this works fine in clean environments, I often find that customers computers are not so clean and one of the first problem areas is the introduction of an unwanted Proxy with causes my application not to run. I get alot of bad press that the application does not work well, when in reality it is a result of a hidden issue on the customer machine.
When I go to query my endpoints the proxy interferes and I lose all communications with the Service.
I am thinking of going back to WCF and using namedpipes but before I do so, wondered if there was a better way in the ServiceStack world (Which I absolutely love)
Ideas? Suggestions?
If a local HTTP proxy is causing issues one thing you could try is to use SSL which will let you tunnel your traffic as an opaque binary through their proxy minimizing potential for interference.
Configuring SSL for HttpListener is configured the same way for all HttpListener's, i.e. it's not specific to ServiceStack - and it needs to be configured on the OS where it's run.
This answer shows how to configure SSL on Windows: https://stackoverflow.com/a/11457719/85785
You'll be able to use https with ServiceStack HttpListener self-host by following the steps above, I used "https://*:8443/" for the url and "CN=localhost" to bypass the SSL browser warning dialog.
It's not specifically clear in the answer but you can get the Thumbprint from the details tab of the certificate where you then need to remove spaces. If it's easier, you can follow the walkthrough in the answer below to use MMC to import the certificate: https://stackoverflow.com/a/33905011/85785
Situation: We have a web application running on a server. This application needs to fetch data from some other PC(Clients), which are on a different network.
On the clients' pc there are WCF hosted in Windows Services using its their local Sql db. i want to make duplex communication between server and clients for share data with each other.
data share mean share data-table,data-set,string etc between clients and server .
Problem :
1) I have no control over the firewall, proxy, NAT on the client side PC. Mostly company Employee PCs have lots of network security e.g firewall block ICMP traffic and some port too, some Router might be Disabled port-forwarding etc etc , client can change network place.
I don't want to make any setting on client side Router,proxy,firewall though .
during communication how can i handle that's kind of issue of client side?
as you know skype is working perfect in that situation.
firewalls very often block inbound connections to clients; the client may not be reachable from the server, it may be using NAT translation behind a router and so cannot be contacted without port forwarding being set up on the router and some new router disabled port forwarding .
2) On clients side there is no IIS .
I don't want to allow remote access on clients PC.
There are more than 100 Clients and only one Server. one server need communicate with many clients on different network .
3) One side my client application is using window application and wcf hosted in window service ,Other side on my server i'm using Web application . so its mean communication is between desktop pc and web pc , that's issue .
If both using a web application then it was not issue to make duplex communication.because i know WEBRTC is fit there lol.
Technology which i had already test and find issue
WSDualHttpBinding: Not work if client behind NAT. check this for detail click here
MSMQ : its bad technique if clients more than 1 and performance issue also because its use RAM memory . check here click here
Xsocket: Its also not work if ICMP traffic block by firewall on client. check here click
WebRTC: Its work fine but its support web to web communication .as my client side i have win app.
Socket.io: Its need to set up node.js and many other thing , hard to implement because i need implement on existence application , i am not making new application.
C# Socket Program: Its wouldn't work if client behind NAT.check here click for detail
Service Bus relay: Its not free even for testing .
socketPro: I studied i find its good but i can't find any right sample on google .so that i could test that.
Genuine Channels: I can't find any sample on google .
Lets see SignalR issue .: Server side i run a console application and Client side i run two application ,one is console and other web. when i was running console client application than it was not initiating connection with Server but when i was using web client application then it was working fine.
sample link is here SignalR two way communication
I can't understand why thas??
Please tell me What is best most secure and fast way to handle this situation? what approach should i use ?
SignalR seems to fit for this solution, because it's flexible.
It negotiates the fastest available channel of communication and that is what you are looking for.
You should investigate the problem with it and signalR will eventually work.
I'm using SignalR extensively to communicate between the servers (C#), between server and mobile apps (C#, Xamarin, iOS, Android). The servers are at different locations and the mobile apps can be anywhere. It all works very reliable.
Take a look at: http://www.asp.net/signalr/overview/deployment/tutorial-signalr-self-host and here http://www.asp.net/signalr/overview/guide-to-the-api/hubs-api-guide-net-client
I've been working in my spare time with sockets (admittedly in c++, not c# but there shouldn't be a difference), and I've never had an issue connecting to clients behind a firewall/router, even without port forwarding.
Routers and firewalls generally don't like server-like programs, eg. programs that bind the socket to a port number. Does your client do anything related to binding? Because it shouldn't.
Needless to say, I would suggest a socket program. The way I see it, it's the most flexible way.
I have been doing research for a few months now on the possibility of client-server communication. I have experimented with many methods such as WebORB and FluorineFX, which are both servers designed to deal with client/server authentication.
WebORB only runs on Windows for their .NET version as far as I can tell, and I would much rather use an open source system. I have tried using FluorineFX, but I think their must be a simpler way for me to build my own simple system from the ground up.
I have been using Dropbox for a while now, and I like the way that the client-server communication is instant. As far as I can tell (from some Google searches) the client doesn't open a port of its own, and just communicates with the Dropbox server through port 80. An example of its instant communication is where you may delete a file on Dropbox on their website, and instantly the server communicates with the client telling it what has happened. I don't know how this instant communication is possible without opening a port.
I can create a system that uses fetching from the client, asking the server every 10 seconds or so to see if there are any updates, but I would like a method to be able to push the information from the server to the client.
My server runs Linux so I don't think I can use WCF, and ideally I am looking for a way to make PHP and C# communicate with each other.
I would love to hear any advice that anyone has and how they deal with the problem.
Cheers.
You CAN use WCF to communicate with any platform. Just make sure you're using an endpoint which your target machine support: http://msdn.microsoft.com/en-us/library/ms733107.aspx
Have you tried the good old .NET Remoting which runs perfectly with Mono?
You can choose between a TcpChannel (for performance) and a HttpChannel (to pass proxy/firewall easily).
For push notifications, you can open a connection to your server and wait for an answer indefinitely.
I hope someone can guide me as I'm stuck... I need to write an emergency broadcast system that notifies workstations of an emergency and pops up a little message at the bottom of the user's screen. This seems simple enough but there are about 4000 workstations over multiple subnets. The system needs to be almost realtime, lightweight and easy to deploy as a windows service.
The problem started when I discovered that the routers do not forward UDP broadcast packets x.x.x.255. Later I made a simple test hook in VB6 to catch net send messages but even those didn't pass the routers. I also wrote a simple packet sniffer to filter packets only to find that the network packets never reached the intended destination.
Then I took a look and explored using MSMQ over HTTP, but this required IIS to be installed on the target workstation. Since there are so many workstations it would be a major security concern.
Right now I've finished a web service with asynchronous callback that sends an event to subscribers. It works perfectly on a small scale but once there are more than 15 subscribers performance degrades considerably. Polling a server isn't really an option because of the load it will generate on the server (plus I've tried it too)
I need your help to guide me as to what technology to use. has anyone used the comet way with so many clients or should I look at WCF?
I'm using Visual C# 2005. Please help me out of this predicament.
Thanks
Consider using WCF callbacks mechanism and events. There is good introduction by Juval Lowy.
Another pattern is to implement blocking web-service calls. This is how GMail chat works, for example. However, you will have to deal with sessions and timeouts here. It works when clients are behind NATs and Firewalls and not reachable directly. But it may be too complicated for simple alert within intranet.
This is exactly what Multicast was designed for.
A normal network broadcast (by definition) stays on the local subnet, and will not be forwarded through routers.
Multicast transmissions on the other hand can have various scopes, ranging from subnet local, through site local, even to global. All you need is for the various routers connecting your subnets together to be multicast aware.
This problem i think is best solved with socket.
Open a connection to the server, and keep it open.
Could you have a slave server in each subnet that was responsible for distributing the messages to all the clients in the subnet?
Then you could have just the slaves attached to the central server where the messages are initiated.
I think some of you are vastly overthinking this. There is already a service built into every version of Windows that provides this exact functionality! It is called the Messenger service. All you have to do is ensure that this service is enabled and running on all clients.
(Although you didn't specify in the question, I'm assuming from your choices of technology that the client population of this network is all Windows).
You can send messages using this facility from the command line using something like this:
NET SEND computername "This is a test message"
The NET SEND command also has options to send by Windows domain, or to specific users by name regardless of where they are logged in, or to every system that is connected to a particular Windows server. Those options should let you easily avoid the subnet issue, particularly if you use domain-based security on your network. (You may need the "Alerter" service enabled on certain servers if you are sending messages through the server and not directly to the clients).
The programmatic version of this is an API called NetMessageBufferSend() which is pretty straightforward. A quick scan of P/Invoke.net finds a page for this API that supplies not only the definitions you need to call out to the API, but also a C# sample program!
You shouldn't need to write any client-side code at all. Probably the most involved thing will be figuring out the best set of calls to this API that will get complete coverage of the network in your configuration.
ETA: I just noticed that the Messenger service and this API are completely gone in Windows Vista. Very odd of Microsoft to completely remove functionality like this. It appears that this vendor has a compatible replacement for Vista.