Please excuse my lack of experience, I'm not sure where to begin, I'm googling my self in circles.
Would it be possible to create a socket server (c#) console application and host it on a goDaddy shared hosting account. I'm trying to create a server/client application but I'm stuck with a shared hosting account from goDaddy.
Also, is there a significant difference between sockets and webSockets?
If you could point me in the right direction, or at the very least let me know if its even possible...?
EDIT:
I have a WPF application running of a windows surface tablets (3 tablets), the application is for time tracking, it gives people the ability to login / logout using an RFID reader. For the backend I'm using Web API and the issue is latency. It sometimes takes up to 15 seconds for the application to create a connection, authenticate (if not authenticated) and get the person's status.
Needless to say staff are impatient and I see their point (they should be able to swipe, confirm and walk away), I'd like to be under 2 seconds max. So I figured if I can keep a connection open through-out operating hours (sockets), then fetching a user's status should be near instantaneous.
I'm open to any suggestion/recommendation. I can't thank you enough! Thnx a million!
Without getting into some rather hinkey maneuvers that would probably get your account shut down you would be very hard pressed to run a socket server on godaddy shared hosting. Mechanically you'd need to be able to execute a custom .exe which would need to be executed -- and kept executing -- by something somewhere. This executable would also need to listen on a particular TCP port which would most likely be either in use like ports 80 and 443 or would likely be firewalled from the rest of the world.
Hosting a web socket app would be tricky -- first they would need to have ugraded to IIS 8 and cursory tests indicate they are still on IIS 7.5. Second, they would need to permit websocket usage which is not something likely to be enabled on shared hosts. I think resource usage would be a challenge if you managed to run these two traps.
It would help quite a bit to understand what you are doing but if it is something that requires either sockets or even web sockets you are looking at a class of hosting above the godaddy shared options.
Related
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 am planning a SaaS system, to be written in C#, ASP.NET using WCF that has two separate components:
On a static IP web server in the cloud will be a web app, common to all clients.
Inside each client's office will be another app, installed on a server with IIS.
The site app will obviously be able to connect to the web services published on the web site. But here's the rub - I also want the web app to be able to initiate a connection to the site app... and the on-site server may not necessarily have a static IP. I can't control this, because we may have hundreds of clients at some point in the future, and we cannot limit our saleability by insisting that the customer has a server with fixed IP.
So, how to do this?
I could have the site apps "checking in" with the web every minute or so, to give the web app the possibility of responding with a "while you're here, please do x,y,z..." but that seems very inelegant. Also, if we're talking about hundreds of clients, I don't want to be bombarding my web server with all these "hi there!" messages if they're not actually required.
Is there a better way?
WCF? Here we go:
Use a message based approach (exchange message, no stateful method calls).
Clients connect to the server. Establish a HTTP-based TWO WAY CONNECTION. This way the server can call back to connected clients. This is standard WCF stuff and works well through NAT with version 4 of the .NET framework.
Voila. In case of a disconnect the client can re-connect, re-identify himself and gets the pending messages.
IIRC "push communication" is done by letting the client do a HTTP Request with an indefinate timeout. Then the server responds when he has something to say. After the respons the client immediately makes a new request.
It works out the same way like the server is making the connection and takes far less resources than polling.
Dynamic DNS is one possibility, but depends on your clients/customers.
If the site app is created by you, it only has to contact the web server when its address has changed (or when the site server/web app is restarted). Still, a keep-alive heart beat of, say, every 30 min. to 1 hour isn't a bad idea.
Edit: I think SNMP services may provide the answer but I'm not a networking expert. You'll have to do some digging or ask a separate question on stackoverflow.
What would you say about Comet technology?
Sounds like you'll definitely need some sort of registry on the server, then it could attempt to call out to the client apps if it needs work doing.
Generally it is client apps that check in with the server every X seconds - this is how Selenium grid works anyway. With a central hub with which clients register. When the hub receives a request to run some tests it passes the jobs out to the clients to perform.
You may not need the "checking in". The server could just attempt to call out to a registered client app until it finds one that is available.This way only the server would need a static address (could use a DNS name instead of an IP to make it more robust).
Also have a look at XMPP PubSub. This could be a more robust and standardised way to handle this.
In the end I decided to go with NetTcpBinding, for reasons best given by #Allon Guralnek here. It's worth clicking through and reading what he has to say...
What might be the considerations for building a real time screen sharing service (some where close to shared view or live meeting) on top of Windows Azure? Please share your thoughts.
For this, it is obvious that we've to create a custom TCP/IP server - to which clients can connect to and exchange (publish/retrieve) data real time, over a custom protocol on top of TCP/IP.
I think Azure supports TCP/IP only for the web role as of now, on port 80 and 443? Please share your thoughts.
Wow - almost 2 years old and no accepted answer! As Joannes stated, realtime is going to be a challenge - you'll need to carefully evaluate what that means to you in terms of response time and latency.
Windows Azure Worker and Web Roles have evolved considerably since you asked this. You can now have up to 25 input (e.g. external-facing) endpoints in your deployment, spread across any combination of Web and Worker roles - you define the port #s - you're not limited to 80 and 443. You may also have up to 25 Internal endpoints (used for inter-role communication).
Designing to run a desktop-sharing service in Windows Azure would have the same basic considerations as when designing for Windows Server (that's what the Windows Azure VMs are running, afterall - Windows Server 2008 R2). You'll need to deal with authentication and authorization, through your own custom solution or possibly with Access Control Services.
Ok, there "is" one thing you'll need to keep in mind: Windows Azure VMs are stateless, and you shouldn't assume a user will always connect to the same VM instance (there's no way to direct-access a specific instance of a Web or Worker role). So, you'll need to externalize any type of session-specific data (which is very easy, with both SQL Azure and Windows Azure Cache service both very simple to set up and use as session providers).
Low latency is still a tough case for cloud computing providers (Azure being no exception). I think that's going to toughest part in the design. Then, since the Nov'09 release, worker roles can have entry points too (not sure about port limitations though).
I have 50+ kiosk style computers that I want to be able to get a status update, from a single computer, on demand as opposed to an interval. These computers are on a LAN in respect to the computer requesting the status.
I researched WCF however it looks like I'll need IIS installed and I would rather not install IIS on 50+ Windows XP boxes -- so I think that eliminates using a webservice unless it's possible to have a WinForm host a webservice?
I also researched using System.Net.Sockets and even got a barely functional prototype going however I feel I'm not skilled enough to make it a solid and reliable system. Given this path, I would need to learn more about socket programming and threading.
These boxes are running .NET 3.5 SP1, so I have complete flexibility in the .NET version however I'd like to stick to C#.
What is the best way to implement this? Should I just bite the bullet and learn Sockets more or does .NET have a better way of handling this?
edit:
I was going to go with a two way communication until I realized that all I needed was a one way communication.
edit 2:
I was avoiding the traditional server/client and going with an inverse because I wanted to avoid consuming too much bandwidth and wasn't sure what kind of overhead I was talking about. I was also hoping to have more control of the individual kiosks. After looking at it, I think I can still have that with WCF and connect by IP (which I wasn't aware I could connect by IP, I was thinking I would have to add 50 webservices or something).
WCF does not have to be hosted within IIS, it can be hosted within your Winform, as a console application or as windows service.
You can have each computer host its service within the winform, and write a program in your own computer to call each computer's service to get the status information.
Another way of doing it is to host one service in your own computer, and make the 50+ computers to call the service once their status were updated, you can use a database for the service to persist the status data of each node within the network. This option is easier to maintain and scalable.
P.S.
WCF aims to replace .net remoting, the alternatives can be net.tcp binding or net.pipe
Unless you have plans to scale this to several thousand clients I don't think WCF performance will even be a fringe issue. You can easily host WCF services from windows services or Winforms applications, and you'll find getting something working with WCF will be fairly simple once you get the key concepts.
I've deployed something similar with around 100-150 clients with great success.
There's plenty of resources out on the web to get you started - here's one to get you going:
http://msdn.microsoft.com/en-us/library/aa480190.aspx
Whether you use a web service or WCF on your central server, you only need to install and configure IIS on the server (and not on the 50+ clients).
What you're trying to do is a little unclear from the question, but if the clients need to call the server (to get a server status, for example), then they just call a method on the webservice running on the server.
If instead you need to have the server call the clients from time to time, then you'll need to have each client call a sign-in method on the server webservice each time the client starts up. The sign-in method would take a delegate method from the client as a parameter. The server would then call this delegate when it needed information from the client.
Setting up each client with its own web service would represent an inversion of the traditional (one server, multiple clients) client/server architecture, and as you've already noted this would be impractical.
Do not use remoting.
If you want robustness and scalability you end up ruling out everything but what are essentially stateless remote procedure calls. Since this is exactly the capability of web services, and web services are simpler and easier to build, remoting is an essentially pointless technology.
Callbacks with remote delegates are on the performance/reliability forbidden list, so if you were thinking of using remoting for that, think again.
Use web services.
I know you don't want to be polling, but I don't think you need to. Since you say all your units are on a single network segment then I suggest UDP for broadcast change notifications, essentially setting a dirty flag, and allowing the application to (re-)fetch on demand. It's still not reliable but it's easy and very fast because it's broadcast.
As others have said you don't need IIS, you can self-host. See ServiceHost class for details on how to do this.
I'd suggest using .NET Remoting. It's quite easy to implement and doesn't require anything else.
For me its is better to learn networking.. or the manual way of socket communication.. web services are mush slower because it contains metadata..
your clients and the servers can transform to multithreaded application. just imitate the request and response architecture. it is much easy to implement a network application like this..
If you just need a status update, you can use much simpler solution, such as simple tcp server/client messaging or like orrsella said, remoting. WCF is kinda overkill here.
One note though, if all your 50+ kiosk is connected via internet, then you might need use VPN or have an open port on each kiosk(which is a security risk) so that your server can retrieve status update from each kiosk.
We had a similiar situation, but the status is send to our server periodically, so we only have 1 port to protect/secure. The frequency of the update is configurable as to accomodate slower clients.
As someone who implemented something like this with over 500+ clients and growing:
Message Queing is the way to go.
We have gone from an internal developed TCP server and client to WCF polling and ended up with Message queing. It's the only guaranteed way to get data to and from clients and servers over the internet. As a bonus, many of these solutions have an extensive framework makeing it trivial to implement publish-subscribe, Send-one-way, point-to-point sending, Request-reply. Some of these are possible with WCF but it will involve crying, shouting, whimpering and long nights not to mention gallons of coffee.
A couple of important remarks:
Letting a process poll the clients instead of the other way around = Bad idea.. it is not scalable at all and you will soon be running in to trouble when the process is take too long to complete.. Not to mention having to handle all the ip addresses ( do you have access to all clients on the required ports ? What happpens when the ip changes etc..)
what we have done: The clients sends status updates to a central message queue on a regular interval ( you can easily implement live updates in the UI), it also listens on it's own queue for a GetStatusRequest message. if it receives this, it answers ( has a timeout).. this way, we can see overal status of all clients at all times and get a specific status of a specific client when needed.
Concerning bandwidth: kiosk usually show images/video etc.. 1Kb or less status messages will not be the big overhead.
I CANNOT stress enough that the current design you present will have a very intensive development cycle AND will not scale or extend well ( trust me, we have learned this lesson). Next to this, building a good client/server protocol for this type of stuff is a hard job that will be totally useless afterwards if you make a design error ( migrating a protocol is not easy)
We have built our solution ontop of ActiveMQ ( using NMS library c#) and are currently extending Simple Service Bus for our internal workings.
We only use WCF for the communication between our winforms app and the centralized service(s)
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.