How to Resolve TCP Error Code 10061 in C# WCF Applications

The development of networked applications using Windows Communication Foundation (WCF) in C# often involves myriad challenges and errors. One such error that developers frequently encounter is TCP error code 10061. This frustrating issue arises when there's a failure in establishing a connection between client and server, typically because the server isn't listening on the specified port or isn't reachable at the given endpoint.

Understanding the Problem

When working with WCF services, you may run into the following error message:

TCP error code 10061: No connection could be made because the target machine actively refused it.

This error usually indicates a networking or configuration issue. It occurs when a client attempts to connect to a service but the connection is blocked or the service isn't responding.

Key Causes of TCP Error 10061

The issue may arise due to several reasons, including:

• The WCF service is not started or properly configured.
• Firewall settings are blocking the connection.
• The service endpoint configuration is incorrect.
• Network connectivity issues between client and server.

Solutions to TCP Error 10061

1. Verify Service is Running

Ensure that your WCF service is running. You can do this by:

• Checking the status of the service in IIS Manager, if hosted in IIS.
• Using a configuration file to ensure the service endpoint is correctly defined.

<service name="MyService">
    <endpoint address="net.tcp://localhost:8080/MyService"
              binding="netTcpBinding"
              contract="IMyService" />
</service>

2. Check Firewall and Network Settings

Firewall or network issues can prevent the connection. Make sure:

• The port used by the WCF service is open and not blocked by your firewall.
• Your server and client are on the same network or are configured to allow remote access.

netsh advfirewall firewall add rule name="Open Port 8080" dir=in action=allow protocol=TCP localport=8080

3. Correct Endpoint Configuration

Endpoint configuration in your WCF service should match that in the client application. Ensure that the bindings, addresses, and contracts match. Here's an example configuration for both service and client:

Service Configuration:

<system.serviceModel>
    <services>
        <service name="MyService">
            <endpoint address="net.tcp://localhost:8080/MyService"
                      binding="netTcpBinding"
                      contract="IMyService" />
        </service>
    </services>
</system.serviceModel>

Client Configuration:

<system.serviceModel>
    <client>
        <endpoint address="net.tcp://localhost:8080/MyService"
                  binding="netTcpBinding"
                  contract="IMyService" />
    </client>
</system.serviceModel>

4. Debugging the Connection

Use tools like netstat to verify if the server is listening on the expected port:

netstat -an | find "8080"

This will help determine whether the port is open and the service is accessible.

Conclusion

Resolving TCP error code 10061 involves checking service status, verifying network configurations, and ensuring proper endpoint settings. By following the steps and solutions outlined in this guide, you can resolve this error and successfully establish a connection in your WCF applications.

We encourage you to delve deeper into each solution and explore advanced configurations based on your project's needs. Network programming can be challenging, but with patience and the right approach, such connection errors can be effectively mitigated.