In my office building we have laptops on multiple floors all running a WCF Service. When WCF services communicate with each other, will a message for an out-of-range device automatically reach it by multi-hopping? Does WCF/the WLAN device driver handle this? Or do I have to detect if a device is not contactable/out-of-range and implement hopping in my own service?
As long as you have a connection from your WCF client to the service - yes, all avenues will be used. You shouldn't have to concern yourself with things like what network path your messages take - the network just has to be present and stable for the duration of a call ;-)
There's nothing in WCF to deal with this, really - this should be handled way lower in the network stack, by the driver or the OS.
Short answer
With WCF can do either or both of these:
Rely on an underlying protocol like IP to handle roaming
Use custom channel code that handles retries, roaming, etc the way you want it
No special mechanism for enhancing roaming is provided in the WCF classes Microsoft provides, but the framework itself is easily capable of supporting this seamlessly if you write or find a channel implementation to do this.
Full answer
WCF is not an on-the-wire protocol. It is a framework that allows you to communicate using a wide variety of protocols and network stacks. This allows you to use the same client and server code whether you are using HTTPS, raw TCP, named pipes, or any other protocol.
WCF ships with many channels in the box, and you can add your own. For example if you want to communicate over BlueTooth or IRDA, just create a new channel that talks these protocols and you can use your WCF services over it. These channels can also be found online or purchased from vendors.
Most networking today is done using the IP protocol, and if you are using WCF to communicate between desktop machines you will probably be using some protocol(s) on top of IP, for example TCP or HTTP. In this case, IP's normal routing rules will be used, so if the two machines can exchane IP packets you can communicate using WCF.
So if your WiFi access points allow seamless roaming you will be able to tap into that functionality using WCF.
If your WiFi routing doesn't have seamless roaming, you will have to do some extra work if you want to maintain a connection during roaming. Specifically you will need to create a channel that will respond to a closed connetion by re-resolving the server nane and retrying the request. Of course you will have to use DNS or another protocol so the server can update its registration as its IP address changes.
WCF is flexible enough to allow you to create such a channel and use it without your application code ever realizing it. But nothing like this comes in the box: You would have to build it, or download or purchase it.
it has nothing to do with WCF....
if there is a connection between the computers, on the IP, then the message will get through...
Related
WebRTC signalling is driving me crazy. My use-case is quite simple: a bidirectional audio intercom between a kiosk and to a control room webapp. Both computers are on the same network. Neither has internet access, all machines have known static IPs.
Everything I read wants me to use STUN/TURN/ICE servers. The acronyms for this is endless, contributing to my migraine but if this were a standard application, I'd just open a port, tell the other client about it (I can do this via the webapp if I need to) and have the other connect.
Can I do this with WebRTC? Without running a dozen signalling servers?
For the sake of examples, how would you connect a browser running on 192.168.0.101 to one running on 192.168.0.102?
STUN/TURN is different from signaling.
STUN/TURN in WebRTC are used to gather ICE candidates. Signaling is used to transmit between these two PCs the session description (offer and answer).
You can use free STUN server (like stun.l.google.com or stun.services.mozilla.org). There are also free TURN servers, but not too many (these are resource expensive). One is numb.vigenie.ca.
Now there's no signaling server, because these are custom and can be done in many ways. Here's an article that I wrote. I ended up using Stomp now on client side and Spring on server side.
I guess you can tamper with SDP and inject the ICE candidates statically, but you'll still need to exchange SDP (and that's dinamycally generated each session) between these two PCs somehow. Even though, taking into account that the configuration will not change, I guess you can exchange it once (through the means of copy-paste :) ), stored it somewhere and use it every time.
If your end-points have static IPs then you can ignore STUN, TURN and ICE, which are just power-tools to drill holes in firewalls. Most people aren't that lucky.
Due to how WebRTC is structured, end-points do need a way to exchange call setup information (SDP) like media ports and key information ahead of time. How you get that information from A to B and back to A, is entirely up to you ("signaling server" is just a fancy word for this), but most people use something like a web socket server, the tic-tac-toe of client-initiated communication.
I think the simplest way to make this work on a private network without an internet connection is to install a basic web socket server on one of the machines.
As an example I recommend the very simple https://github.com/emannion/webrtc-web-socket which worked on my private network without an internet connection.
Follow the instructions to install the web socket server on e.g. 192.168.1.101, then have both end-points connect to 192.168.0.101:1337 with Chrome or Firefox. Share camera on both ends in the basic demo web UI, and hit Connect and you should be good to go.
If you need to do this entirely without any server, then this answer to a related question at least highlights the information you'd need to send across (in a cut'n'paste demo).
Are there limitations that would prevent from establishing a tcp/ip socket connection between two distant devices? (Not on the same WiFi LAN.)
[Edit]
I missed this one: http://msdn.microsoft.com/en-us/library/windowsphone/develop/hh202858(v=vs.105).aspx
I'll try it as it seems like the usual client/server snippet, but for WP, so that looks promising.
I don't think you can do this directly device to device due to dynamically assigned IP address visibility etc. You might have to expose a web service on the public internet for this purpose. Basically a web service both devices can see and communicate with. (ex. Heroku, Amazon AWS). One device can keep a blocking connection ("Comet") while the other device initiates connections.
I am publically distributing an application which can be installed on users PC. Client will periodically communicate with the server to send information from the client. Server have to acknowledge the successful receipt of the information. Occasionally, server will do an one way communication with the client. My question is what is the best/failproof/recommended way to do client-server communication when client is massively distributed? I am currently focusing on self-hosted service to do the communication. What precaution should i take if the clients ip address change frequently?
My suggestions are:
Use HTTP or HTTPS on default ports. By massively I understand you will have no control over the network restrictions, firewalls, NAT traversal, etc. Using HTTP(S) and initiating the connections from the clients with simple web requests will save you a lot of trouble.
Use polling at regular/smart intervals to solve your occasional server initiated data transfer. Clients running on workstations wont have a public IP address, let alone a fixed one.
I'm planning on using a wsDualHttpBinding for a WCF service with callbacks. The clients will be a windows form application communicating to the service over the internet. Obviously I have no control over the firewall on the client side, so I'm wondering what is the proper way to set the ClientBaseAddress on the client side?
Right now in my intiial testing I'm running the service and client on the same pc and i am setting the binding as follows
Dim binding As System.ServiceModel.WSDualHttpBinding = Struct.Endpoint.Binding
binding.ClientBaseAddress = New Uri("http://localhost:6667")
But I have a feeling this won't work when deploying over the internet because "localhost" won't translate to the machine address (much less worrying about NAT translation) and that port might be blocked by the clients firewall.
What is the proper way to handle the base address for callbacks to a remote client?
some one tell me if i do not specify ClientBaseAddress then WCF infratructure creates a default client base address at port 80 which is used for the incoming connections from the service. Since port 80 is usually open to firewalls, things should just work.
so just tell me when win form wcf client apps will run then how can i open my custom port like "6667" and also guide me what library or what approach i should use as a result response should come from client side router
to pc and firewall will not block anything. please discuss this issue with real life scenario how people handle this kind of situation in real life. thanks
The proper way is to use TCP transport instead of HTTP transport. Duplex communication over HTTP requires two HTTP connections - one opened from client to server (that's OK) and second opened from server to client. This can work only in scenarios where you have full control over both ends. There is simply too many complications which cannot be avoided just by guessing what address to use like:
Local Windows or third party firewall has to be configured
Permission for application to run - listening on HTTP is not allowed by default unless UAC is turned off or application is running as admin. You must allow listening on the port through netsh or httpcfg (windows XP and 2003) - that again requires admin permissions.
Port can be already used by another application. In case of 80 it can be used by any local web server - for example IIS.
Private networks and network devices - if your client machine is behind the NAT the port forwarding must be configured but what if you have two machines running your application on the same private network? You cannot forward from the same incoming port to two machines.
All these issues can be avoided mostly only when you have control over whole infrastructure. That is the reason why HTTP duplex communication is useful mostly for intranet scenarios and why for example Silverlight offers another implementation where the second connection is not created and Silverlight client instead polls server continuously to check if there is any callback available.
TCP transport requires only single connection from client to server because TCP protocol is natively duplex so the server can call back the client through the same connection. When you deploy a public service you usually have control over infrastructure on the server side so you can make necessary changes in configuration to make it work.
I think this also answers your previous question.
WCF supports several different protocols for communicating. My WCF services are deployed on the same machine only. I just wanted to know whether TCP is more effecient than HTTP or should i go with HTTP?
If your WCF services are on the same machine, use named pipes. I've found this flow chart helpful.
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If your service will only run on the same machine, then try using NetNamedPipeBinding.
Of course, in any case, you should measure the performance you receive using realistic test data.
The advantage of HTTP - Application layer (7 in the OSI model) - is
close to user (human) usage, via text commands (and many responses)
one can use telnet (to a port where an application dialogs via http protocol) for instance and issue some simple commands to dialog with the remote server
the http protocol deals for you with otherwise complex actions
HTTP is (usually) based on TCP (transport) / IP (Network). Thus all the advantages described above bear a performance penalty. You could define yourself an application with a more flexible protocol (at the user/application level) but it usually requires more programming, like dealing with issues that were already included in HTTP. Also, as the name protocol implies, nobody will understand your own protocol if you define one, unlike http. You'll have to design, program and build not only the server side, but also the client side. Clients will have to install your program and use it.
HTTP is built on top of TCP, therefore TCP will be definitely faster. Also HTTP has to parse the text headers which is another bunch of time spent. If your use case allows that, go with TCP.
HTTP is a protocol on top of TCP, so it's most likely faster NOT to add an additional protocol on top. See also the OSI Model.
You can clearly see that HTTP is on top of TCP here:
http://en.wikipedia.org/wiki/OSI_model
OR
even better here:
http://en.wikipedia.org/wiki/TCP/IP_model
As has been said before, TCP is the transmission control protocol, HTTP is a protocol on top. You can create your own custom protocol that could be more efficient as it would not have some of the http baggage. I had to do this to grab frame numbers from a video stream being recorded on a remote computer.