Sorry if this is a dumb question that's already been asked, but I don't even know what terms to best search for.
I have a situation where a cloud app would deliver a SPA (single page app) to a client web browser. Multiple clients would connect at once and would all work within the same network. An example would be an app a business uses to work together - all within the same physical space (all on the same network).
A concern is that the internet connection could be spotty. I know I can store the client changes locally and then push them all to the server once the connection is restored. The problem, however, is that some of the clients (display systems) will need to show up-to-date data from other clients (mobile input systems). If the internet goes down for a minute or two it would be unacceptable.
My current line of thinking is that the local network would need some kind of "ThinServer" that all the clients would connect to. This ThinServer would then work as a proxy for the main cloud server. If the internet breaks then the ThinServer would take over the job of syncing data. Since all the clients would be full SPAs the only thing moving around would be the data - so the ThinServer would really just need to sync DB info (it probably wouldn't need to host the full SPA - though, that wouldn't be a bad thing).
However, a full dedicated server is obviously a big hurdle for most companies to setup.
So the question is, is there any kind of tech that would allow a web page to act as a web server? Could a business be instructed to go to thinserver.coolapp.com in a browser on any one of their machines? This "webpage" would then say, "All clients in this network should connect to 192.168.1.74:2000" (which would be the IP:port of the machine running this page). All the clients would then connect to this new "server" and that server would act as a data coordinator if the internet ever went down.
In other words, I really don't like the idea of a complicated server setup. A simple URL to start the service would be all that is needed.
I suppose the only option might have to be a binary program that would need to be installed? It's not an ideal solution - but perhaps the only one? If so, are their any programs out there that are single click web servers? I've tried MAMP, LAMP, etc, but all of them are designed for the developer. Any others that are more streamlined?
Thanks for any ideas!
There are a couple of fundamental ways you can approach this. The first is to host a server in a browser as you suggest. Some example projects:
http://www.peer-server.com
https://addons.mozilla.org/en-US/firefox/addon/browser-server/
Another is to use WebRTC peer to peer communication to allow the browsers share information between each other (you could have them all share date or have one act as a 'master' etc deepening not he architecture you wanted). Its likely not going to be that different under the skin, but your application design may be better suited to a more 'peer to peer' model or a more 'client server' one depending on what you need. An example 'peer to peer' project:
https://developer.mozilla.org/en-US/docs/Web/Guide/API/WebRTC/Peer-to-peer_communications_with_WebRTC
I have not used any of the above personally but I would say, from using similar browser extension mechanisms in the past, that you need to check the browser requirements before you decide if they can do what you want. The top one above is Chrome based (I believe) and the second one is Firefox. The peer to peer one contains a list of compatible browser functions, but is effectively Firefox and Chrome based also (see the table in the link). If you are in an environment where you can dictate the browser type and plugins etc then this may be ok for you.
The concept is definitely very interesting (peer to peer web servers) and it is great if you have the time to explore it. However, if you have an immediate business requirement, it might be that a simple on site server based approach may actually be more reliable, support a wider variety of browser and actually be easier to maintain (as the skills required are quite commonly available).
BTW, I should have said - 'WebRTC' is probably a good search term for you, in answer to the first line of your question.
httprelay.io v.s. WebRTC
Pros:
Simple to use
Fast
Supported by all browsers and HTTP clients
Can be used with the not stable network
Opensource and cross-platform
Cons:
Need to run a server instance
No data streaming is supported (yet)
Related
I want to create a program for my desktop and an app for my android. Both of them will do the same, just on those different devices. They will be something like personal assistants, so I want to put a lot of data into them ( for example contacts, notes and a huge lot of other stuff). All of this data should be saved on a server (at least for the beginning I will use my own Ubuntu server at home).
For the android app I will obviously use java and the database on the server will be a MySQL database, because that's the database I have used for everything. The Windows program will most likely be written in of these languages: Java, C#c C++, as these are the languages I am able to use quite well.
Now to the problem/question: The server should have a good backend which will be communicating with the apps/programs and read/write data in the database, manage the users and all that stuff. But I am not sure how I should approach programming the backend and the "network communication" itself. I would really like to have some relatively easy way to send secured messages between server and clients, but I have no experience in that matter. I do have programming experience in general, but not with backend and network programming.
side notes:
I would like to "scale big". At first this system will only be used by me, but it may be opened to more people or even sold.
Also I would really like to a (partly) self programmed backend on the server, because I could very well use this for a lot of other stuff, like some automation features in my house, which will be implemented.
EDIT: I would like to be able to scale big. I don't need support for hundreds of people at the beginning ;)
You need to research Socket programming. They provide relatively easy, secured network communication. Essentially, you will create some sort of connection or socket listener on your server. The clients will create Sockets, initialize them to connect to a certain IP address and port number, and then connect. Once the server receives these connections, the server creates a Socket for that specific connection, and the two sockets can communicate back and forth.
If you want your server to be able to handle multiple clients, I suggest creating a new Thread every time the server receives a connection, and that Thread will be dedicated to that specific client connection. Having a multi-threaded server where each client has its own dedicated Thread is a good starting point for an efficient server.
Here are some good C# examples of Socket clients and servers: https://msdn.microsoft.com/en-us/library/w89fhyex(v=vs.110).aspx
As a side note, you can also write Android apps in C# with Xamarin. If you did your desktop program and Android app both in C#, you'd be able to write most of the code once and share it between the two apps easily.
I suggest you start learning socket programming by creating very simple client and server applications in order to grasp how they will be communicating in your larger project. Once you can grasp the communication procedures well enough, start designing your larger project.
But I am not sure how I should approach programming the backend and
the "network communication" itself.
Traditionally, a server for your case would be a web server exposing REST API (JSON). All clients need to do http requests and render/parse JSON. REST API is mapped to database calls and exposes some data model. If it was in Java, it would be Jetty web server, Jackson Json parser.
I would really like to have some relatively easy way to send secured
messages between server and clients,
Sending HTTP requests probably the easiest way to communicate with a service. Having it secured is a matter of enabling HTTPS on the server side and implementing some user access authentication and action authorization. Enabling HTTPS with Jetty for Java will require few lines of code. Authentication is usually done via OAuth2 technique, and authorization could be based on ACL. You may go beyond of this and enable encryption of data at rest and employ other practices.
I would like to "scale big". At first this system will only be used by
me, but it may be opened to more people or even sold.
I would like to be able to scale big. I don't need support for
hundreds of people at the beginning
I anticipate scalability can become the main challenge. Depending on how far you want to scale, you may need to go to distributed (Big Data) databases and distributed serving and messaging layers.
Also I would really like to a (partly) self programmed backend on the
server, because I could very well use this for a lot of other stuff,
like some automation features in my house, which will be implemented.
I am not sure what you mean self-programmed. Usually a backend encapsulates some application specific business logic.
It could be a piece of logic between your database and http transport layer.
In more complicated scenario your logic can be put into asynchronous service behind the backend, so the service can do it's job without blocking clients' requests.
And in the most (probably) complicated scenario your backend may do machine learning (for example, if you would like you software stack to learn your home-being habits and automate house accordingly to your expectations without actually coding this automation)
but I have no experience in that matter. I do have programming
experience in general, but not with backend and network programming.
If you can code, writing a backend is not very hard problem. There are a lot of resources. However, you would need time (or money) to learn and to do it, what may distract you from the development of your applications or you may enjoy it.
The alternative to in-house developed of a backend could be a Backend-as-a-Service (BaaS) in cloud or on premises. There are number of product in this market. BaaS will allow you to eliminate the development of the backend entirely (or close to this). At minimum it should do:
REST API to data storage with configurable data model,
security,
scalability,
custom business-logic
Disclaimer: I am a member of webintrinsics.io team, which is a Backend-as-a-Service. Check our website and contact if you need to, we will be able to work with you and help you either with BaaS or with guiding you towards some useful resources.
Good luck with your work!
*If you think I should ask this question elsewhere, please let me know.
Background:
I need to build an application for converting weights into piece counts. The weights currently come from scales that are connected to PCs via serial ports. I am replacing PC based applications that connect to the scales via a serial connection. I am considering the feasibility of making the next generation of these applications into a web based solution. However, I do not want to do this if it is not a better solution than building an application that runs on the client. In addition, I do not want to use any sort of browser specific technology (ActiveX).
FYI, we currently run a Windows based environment.
What I have so far:
I am currently thinking that I will need some sort of client side “service” to allow the scale data to be retrieved by the web application. I have looked into creating a WCF service for this task and have determined that it would probably work. This would require that the scale be connected to some sort of Windows based computer that is on the network. I would then interface the WCF service (running as a Windows Service on the PC) from an ASP.NET web application running on an IIS web server. This would minimize the footprint on the client and allow us to use a web application.
I am looking for any constructive thoughts and ideas. I am open to reviewing any feasible option that would make this solution as simple and reliable as possible.
Answering my own question per request #honeycomb.
I discovered two viable options for this purpose. Following are high-level overviews of the techniques we leveraged.
Develop a scale reader to be run on a PC connected to the weigh scale device via an RS-232 connection. This reader will forward any information received from the scale into a database. Combined with technologies like change notifications and server-side push notifications, this option will allow data from a weigh scale to be pushed into a web page with little effort and no additional cost. (This option has performed well during testing but is not yet in production)
Invest in converting weigh scale devices to use ethernet connections and connect them to the network. Use an OPC server with a driver that can connect to the weigh scales you are using to read the data from these devices. Consider KEPWare's offering for this purpose. Use KEPWare's tools to forward this data to a database or wherever it is needed. Once again, you can leverage change notifications and server-side push technologies to push this data into web applications in near real-time without polling. (This option is currently working in a critical, production environment)
The second option is probably better in the long-term, but this may vary based on your specific situation. It has some up front costs and would be better suited to new implementations. For my system, I am using the first option because it will ease the transition between the new and old systems.
Note: I am not in any way associated with KEPWare. I am only suggesting their product because it is the only one I am aware of that supports this functionality. I am sure there are other OPC servers that support this type of device.
I am searching for a good method to transfer data over internet, and I work in C++/windows environment. The data is binary, a compressed blob of an extracted image. Input and requirements are as follows:
6kB/packet # 10 packets/sec (60kBytes per second)
Reliable data transfer
I am new to network programming and so far I could figure out that one of the following methods will be suitable.
Sockets
MSMQ (MS Message Queuing)
The Client runs on a browser (Shows realtime images on browser). While server runs native C++ code. Please let me know if there are any other methods for achieving the same? Which one should I go for and why?
If the server determines the pace at which images are sent, which is what it looks like, a server push style solution would make sense. What most browsers (and even non-browsers) are settling for these days are WebSockets.
The main advantage WebSockets have over most proprietary protocols, apart from becoming a widely adopted standard, is that they run on top of HTTP and can thus permeate (most) proxies and firewalls etc.
On the server side, you could potentially integrate node.js, which allows you to easily implement WebSockets, and comes with a lot of other libraries. It's written in C++, and extensible via C++ and JavaScript, which node.js hosts a VM for. node.js's main feature is being asynchronous at every level, making that style of programming the default.
But of course there are other ways to implement WebSockets on the server side, maybe node.js is more than you need. I have implemented a C++ extension for node.js on Windows and use socket.io to do WebSockets and non-WebSocket transports for older browsers, and that has worked out fine for me.
But that was textual data. In your binary data case, socket.io wouldn't do it, so you could check out other libraries that do binary over WebSockets.
Is there any specific reason why you cannot run a server on your windows machine? 60kb/seconds, looks like some kind of an embedded device?
Based on our description, you ned to show image information, in realtime on a browser. You can possibly use HTTP. but its stateless, meaning once the information is transferred, you lose the connection. You client needs to poll the C++/Windows machine. If you are prety confident the information generated is periodic, you can use this approach. This requires a server, so only if a yes to my first question
A chat protocol. Something like a Jabber client running on your client, and a Jabber server on your C++/Windows machine. Chat protocols allow almost realtime
While it may seem to make sense, I wouldn't use MSMQ in this scenario. You may not run into a problem now, but MSMQ messages are limited in size and you may eventually hit a wall because of this.
I would use TCP for this application, TCP is built with reliability in mind and you can simply feed data through a socket. You may have to figure out a very simple protocol yourself but it should be the best choice.
Unless you are using an embedded device that understands MSMQ out of the box, your best bet to use MSMQ would be to use a proxy and you are then still forced to play with TCP and possibly HTTP.
I do home automation that includes security cameras on my personal time and I use the .net micro framework and even if it did have MSMQ capabilities I still wouldn't use it.
I recommend that you look into MJPEG (Motion JPEG) which sounds exactly like what you would like to do.
http://www.codeproject.com/Articles/371955/Motion-JPEG-Streaming-Server
I'm coding an extension for a customer, one of the requirements is that the extension also works offline because internet services are not that reliable, my customer's business can't stop but can deal with "stale" data, thats a nice tradeoff I guess.
Therefore, I want to code some kind of distributed cache as an extension to synchronize local data among the N nodes that will be connected running the same application and thus synchronize with the real database, hosted on the internet.
In order to achieve that I imagined that I would need to make a network broadcast and listen to incoming broadcasts, then every node that starts to run my application will broadcast it's IP address and become available as a new node for the distributed cache, failover is very important here.
I googled some possibilities I initially thought but none of them will work, I guess. The first was to do it just with HTTP, the second was to use Google Native Client to write C++ code that could run network code and thus do the broadcast, but it has limitations. Right now I'm thinking to use Java Applets but I don't really know if they have some limitations related to networking or if Chrome Extensions has any limitation with Java Applets.
Any ideas on how to do it? Using some of the stuff I suggested or another approach?
You could create an NPAPI extension, which would not be restricted by Chrome at all.
I'm making a network game (1v1) where in-game its p2p - no need for a game server.
However, for players to be able to "find each other", without the need to coordinate in another medium and enter IP addresses (similar to the modem days of network games), I need to have a coordination/matching server.
I can't use regular web hosting because:
The clients will communicate in UDP.
Therefore I'll need to do UDP Hole Punching to be able to go through the NAT
That would require the server to talk in UDP and know the client's IP and port
afaik with regular web hosting (php/etc) I can only get the client's IP address and can only communicate in TCP (HTTP).
Options I am currently considering:
Use a hosting solution where my program can accept UDP connection. (any recommendations?)
UDPonNAT seems to do this but uses GTalk and requires each client to have a GTalk account for this (which probably makes it an unsuitable solution)
Any ideas? Thanks :)
First, let me say that this is well out of my realm of expertise, but I found myself very interested, so I've been doing some searching and reading.
It seems that the most commonly prescribed solution for UDP NAT traversal is to use a STUN server. I did some quick searches to see if there are any companies that will just straight-up provide you with a STUN hosting solution, but if there even were any, they were buried in piles of ads for simple web hosting.
Fortunately, it seems there are several STUN servers that are already up and running and free for public use. There is a list of public STUN servers at voip-info.org.
In addition, there is plenty more information to be had if you explore SO questions tagged "nat".
I don't see any other choice than to have a dedicated server running your code. The other solutions you propose are, shall we say, less than optimal.
If you start small, virtual hosting will be fine. Costs are pretty minimal.
Rather than a full-blown dedicated server, you could just get a cheap shared hosting service and have the application interface with a PHP page, which in turn interfaces with a MySQL database backend.
For example, Lunarpages has a $3/month starter package that includes 5gb of space and 50gb of bandwidth. For something this simple, that's all you should need.
Then you just have your application poll the web page for the list of games, and submit a POST request in order to add their own game to the list.
Of course, this method requires learning PHP and MySQL if you don't already know them. And if you do it right, you can have the PHP page enter a sort of infinite loop to keep the connection open and just feed updates to the client, rather than polling the page every few seconds and wasting a lot of bandwidth. That's way outside the scope of this answer though.
Oh, and if you're looking for something absolutely free, search for a free PHP host. Those exist too! Even with an ad-supported host, your app could just grab the page and ignore the ads when you parse the list of games. I know that T35 used to be one of my favorites because their free plan doesn't track space or bandwidth (it limits the per-file size, to eliminate their service being used as a media share, but it shouldn't be a problem for PHP files). But of course, I think in the long run you'll be better off going with a paid host.
Edit: T35 also says "Free hosting allows 1 domain to be hosted, while paid offers unlimited domain hosting." So you can even just pay for a domain name and link it to them! I think in the short term, that's your best (cheapest) bet. Of course, this is all assuming you either know or are willing to learn PHP in order to make this happen. :)
There's nothing that every net connection will support. STUN is probably good, UPnP can work for this.
However, it's rumored that most firewalls can be enticed to pass almost anything through UDP port 53 (DNS). You might have to argue with the OS about your access to that port though.
Also, check out SIP, it's another protocol designed for this sort of thing. With the popularity of VOIP, there may be decent built-in support for this in more firewalls.
If you're really committed to UDP, you might also consider tunneling it over HTTP.
how about you break the problem into two parts - make a game matcher client (that is distinct from the game), which can communicate via http to your cheap/shared webhost. All gamers who wants to use the game matching function use this. THe game matcher client then launches the actual game with the correct parameters (IP, etc etc) after obtaining the info from your server.
The game will then use the standard way to UDP punch thru NAT, etc etc, as per your network code. The game dont actually need to know anything about the matcher client or matcher server - in the true sense of p2p (like torrents, once you can obtain your peer's IPs, you can even disconnect from the tracker).
That way, your problems become smaller.
An intermediate solution between hosting your own dedicated server and a strictly P2P networking environment is the gnutella model. In that model, there are superpeers that act like local servers, having known IP addresses and being connected to (and thus having knowledge of) more clients than a typical peer. This still requires you to run at least one superpeer yourself, but it gives you the option to let other people run their own superpeers.