Problem with configuring and starting WCF service

问题

I have a problem with configuration and starting WCF service. In my application there is a method that starts service. Something like this

void Start(string protocol, string address, string port)
{
    host = new ServiceHost(_myService,
        new Uri(String.Format("{0}://{1}{2}/Sample", protocol, address, port)));
    //...Some configuration (bindings, behaviors, etc.)
    host.Open();
}

Let my computer has an IP 192.168.0.1. When I pass 'address' parameter with a value '192.168.0.2' an error occurred

"A TCP error (10049: The requested address is not valid in its context.)
 occurred while listening on IP Endpoint=192.168.0.2:1234"

That's right because it's not my IP. But after that if I pass correct value (my real IP) I get the same error about IP 192.168.0.2! So I can't reconfigure and restart server without restarting application.

Why does it happen? How can I avoid such behavior?

回答1:

I can't see from your question how you are adding the correct endpoint, but I suspect you are attempting to modify the endpoint address. With WCF services, you cannot make changes to the endpoint address after calling

host.Open();

because at this point the service is (if you have no errors) up and accepting requests from clients at the specified address and port number.

You need to create a new ServiceHost object with the correct endpoint address (and dispose of the old one) if you wish to host the service at a new address.

EDIT:

After playing around with the example solution you have posted, I have found a solution to the issue. I think something is going wrong because you are using the same port number for both tries (in the example solution I downloaded you don't specify this, so the port defaulted to 808). The error you are experiencing vanishes if you change your code as follows to specify a different port number in the base address for the 2nd try:

 try
        {
            var host2 = CreateServiceHost("localhost:5432", serviceImpl);

            Console.WriteLine("#2, config: " + host2.BaseAddresses.First().ToString());

            host2.Open();
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }

There seems to be something buggy underneath WCF itself, probably on a socket level, where the port is somehow still unavailable after the first error with the incorrect IP.

I did a quick google and found this article where someone experienced a delay in reusing a port after closing a socket. If you always need to use the same port number, perhaps you could wait a certain amount of time for the port to become free again before trying to create the service host again.

回答2:

Looks like WCF caches a socket object in class ExclusiveTCPTransportManager.

It's seems to be good solution for me:

public static class WCFBugWorkaround
{
    public static bool IsConnectionPossible(this ServiceHost host)
    {
        try
        {
            foreach (var baseAddress in host.BaseAddresses)
            {
                IPAddress[] ipAddresses = Dns.GetHostAddresses(baseAddress.DnsSafeHost);
                IPAddress ipAddr = ipAddresses.Where(e => e.AddressFamily == AddressFamily.InterNetwork).FirstOrDefault();

                if (ipAddr == null)
                {
                    return false;
                }

                using (Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
                {
                    System.Net.IPEndPoint localEP = new IPEndPoint(ipAddr, baseAddress.Port);
                    s.Bind(localEP);
                }
            }
        }
        catch (Exception ex)
        {
            return false;
        }

        return true;
    }
}

ServiceHost host = ...;

...

if (host.IsConnectionPossible())
{
    host.Open();
}

Thank's to Francheska for showing me the right direction :)

来源：https://stackoverflow.com/questions/6649565/problem-with-configuring-and-starting-wcf-service

标签

.net

wcf

configuration