I'm building a WCF P2P service using the PNRP functionality.
I see that I can assign a port to the Bindings... but most of the examples do not.
Is there a reason I should or shouldn't give it a port?
If you don't assign a port, WCF will choose a random available port automatically. The local port information is broadcast to peers as part of the PNRP process, so setting a local port explicitly is more to make your application predictable than anything else.
I usually set my ports explicitly so that I can document them to my customers. This is especially important when a customer uses a 3rd party firewall that I can't easily configure in code. If your app assigns a random port, they won't know what port to unblock in their firewall software.
Related
I'm looking for suggestions about approaches to allow multiple applications to use port 80 for communication.
I know it's impossible, or at lease not sensible to have multiple applications to actually bind to port 80, however, I've seen appliances when there is a device that provides both a web interface (HTTP) and RTSP with RTP using port 80.
I have two ideas on how this is achieved:
Are those custom made apps that implement all the functions?
For example the same binary is used for a web server and a RTSP server. That seems kind of limiting due to the fact that you would have to do sever modifications to already developed apps if you want, for example, Apache and openSSH both on port 80.
Are there a "port 80 multiplexers" sort of a pattern?
For example, a parser application that listens to port 80 and depending on the header of the received package, passes the package to the required application.
Found some related references, will give them a try.
https://bbs.archlinux.org/viewtopic.php?id=99457
http://www.rutschle.net/tech/sslh.shtml
I really don't think this is possible in a standard way: port number is actually the one that allows multiplexing among different applications in TCP and UDP protocols. More generic, TSAP, Transport Service Access Point allows multiplexing at the transport layer. TSAP is the port in protocols such as TCP, UDP, or SCTP.
One reason you may want two applications listening on the same port is that a second application can monitor or process in some other way the messages received, and eventually processed, by the first one. In this case, using pcap library other applications could read messages received by the main application that will probably response those messages.
Netfilter can also be useful, http://www.netfilter.org/
However, if you intend two applications to respond messages that arrive to the same port, that would be tricky and would have dependency on each application.
In this response I'm assuming you are thinking of applications listening to the same port at the same IP address. Something different is working with multihost servers where two applications could listen to same port number in different IP addresses.
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.
I have two processes running on the same machine. Each process is hosting a WCF service to allow inter process communications asynchronously. As of now, I have assigned a fixed port 8731 and 9000 to the two wcf services. What if a customer machine has these ports taken up? How can i dynamically make the wcf client find the wcf service if I were to dynamically allocate an available port?
Thanks for your help in advance.
I assume you're creating services in code. If you're afraid of the client not having those ports available, you should configure your endpoints using app.config. That way, if a client has an issue with a port, you can simply change their config file instead of recompiling your code.
I am late on this post, but today we have better solution for this problem.
There is a configuration endpoint known as listenUriMode(https://msdn.microsoft.com/en-us/library/system.servicemodel.description.listenurimode(v=vs.110).aspx), if we set this value to "Unique", it will bind hostname to port 0 which will ask OS to assign a free port.
Now client can know about the server port using WCF discovery(https://learn.microsoft.com/en-us/dotnet/framework/wcf/feature-details/wcf-discovery-overview).
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...
Doesn’t the dynamic ports keep changing? If yes, wont these ports change and communication stop? Please advice.
If I understand your question, then in short, no.
When your HTTP client (aka web browser) opens a connection the operating system picks a random port number from the dynamic (or "ephemeral") range.
All of the communications for that connection continue to use that same port.
Only when a new connection is opened is another port chosen.
To clarify the other end...
Servers of "standard application protocols", like HTTP and FTP have a port assigned to them by a standards body IANA. For example, in the case of HTTP, the default port is "80".
Unless the client selects a non-standard port, web connections are always made to port 80.
The web server is always listening on port 80, it never goes anywhere.
Separately, some protocols use "dynamic protocol assignment", where the protocol number of a service can change, but there is a way to make sure the changing port number is known.