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WCF Discovery with UDP

Inorder to call the WindowsCommunicationFoundation service, a port or pipe which assigned to the service must be available and the client must know the address endpoints before calling the services.

If the service could use any available address then client can discover that address at runtime. There is a industry standard-based solution which helps in discovering the service addresses.

Address Discovery

Discovery relies on the User Datagram Protocol(UDP). Client uses UDP to broadcast discovery requests for any end-point which supports the contract type. These requests are received by dedicated end-points. The end-points responds back to the client with service-address that support specified contract.

WCF offers a standard discovery endpoint with the type UdpDiscoveryEndpoint

public class DiscoveryEndpoint : ServiceEndpoint

public class UdpDiscoveryEndpoint : DiscoveryEndpoint

Adding ServiceDiscoveryBehavior the service

ServiceHost host = new ServiceHost(....);
host.AddServiceEndpoint(new UdpDiscoveryEndpoint());

Adding ServiceDiscoveryBehavior to service using config file

  <service name="MyService">
    <endpoint kind= "udpDiscoveryEndpoint" />

If you want dynamic base address for your service, the above code is still not perfect as it is requires to add discovery in config file or through code.

Auto Enabling the Discovery through code

public static class DiscoveryHelper
  public static Uri AvailableIpcBaseAddress
  {get; }

  public static Uri AvailableTcpBaseAddress
  {get; }
Uri baseAddress = DiscoveryHelper.AvailableTcpBaseAddress;

ServiceHost host = new ServiceHost(typepf(MyService),baseAddress);

If the host has not already defined the endpoints for the service, EnableDiscovery will add the default endpoints.

Client-Side Code for Discovering end-points

The client uses the DiscoveryClient class to discover all endpoint addresses of all services that support specified contract:

public sealed class DiscoveryClient : ICommunicationObject
   public DiscoveryClient();
   public DiscoveryClient(string endpointName);
   public DiscoveryClient(DiscoveryEndpoint discoveryEndpoint);
   public FindResponse Find(FindCriteria criteria);


Discovering and Invoking an Endpoint

DiscoveryClient discoveryClient = new
DiscoveryClient(new UdpDiscoveryEndpoint() );
FindCriteria criteria = new FindCriteria(typepf(IMyContract));
FindResponse discovered = discoveryClient.Find(criteria);
//Just grab the first found
EndpointAddress address = discovered.Endpoints[0].Address;
Binding binding = new NetTcpBinding();
IMycontract proxy = ChannelFactory<IMycontract>.CreateChannel(binding.address);

Client may discover multiple endpoints supporting the desired contract, it simply invokes the first one in the returned collection.

About the author

Kalyan Bandarupalli

My name is kalyan, I am a software architect and builds the applications using Microsoft .NET technologies. Here I am trying to share what I feel and what I think with whoever comes along wandering to Internet home of mine.I hope that this page and its contents will speak for me and that is the reason I am not going to say anything specially about my self here.

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