Socket.Connect gernerates Execption A socket operation was attempted to an unreachable network.

Question

I've seen quite a few other posts on this exception, but none of them helped me to resolve my issue. I can make the connection just fine using telnet, but when my application attempts to connect to the same address and port, I get the A socket operation was attempted to an unreachable network, exception. The environment the application is running in does not allow ICMP traffic and that seems to be the only thing different. The route exists from the server to the default gateway, and I've been assured that the route is known by the gateway. So why am I unable to make this connection?

You can see the Telnet traffic captured by wireshark here:

But the application gets an exception:

and I see nothing in the wireshark capture.

There's nothing interesting about my code, I've stripped it out of the larger application just to test the TcpClient.Connect() (I've also tested using Socket.Connect()) I've boiled the code down to resemble the examples for using both of these methods presented in the Microsoft documentation.

Connection = new TcpClient(LocalEndPoint);  
Connection.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.DontLinger, true);  
Connection.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);  
Connect();  

Any help provided to resolve this issue would be much appreciated.

Answer 1

so does telnet to 192.168.246.135:8284 work?

Answer 2

Yes it does, and I've stumbled upon the fix since I posted the question. Long and frustrating story short, I was binding the tcp client to IpAddress.Loopback instead of IpAddress.Any. This is why it was working in my local tests and not in my dev environment tests. Sometimes you're just too close to your own code to see the mistakes.

Answer 3

Hi. Thank you for your question and reaching out.

Try resetting the TCP/IP Stack.

STEP 1. Access the command window as an administrator.
STEP 2. We will now run a number of commands in the command window.
STEP 3. To test the TCP/IP configuration, use the first command.
netsh int ip reset

STEP 2. Using the second command, the present IP configuration will be removed.
ipconfig /release

STEP 3. An IP address will be reset using the third instruction.
ipconfig /renew

STEP 4. The faulty or erroneous DNS cache will be cleared by the fourth command.
ipconfig /flushdns

STEP 5. Finally, the primary command to repair any socket issues in the system
netsh winsock reset

STEP 6. Any network troubles with your system will be fully fixed by the following set of commands.
STEP 7. Your computer should be restarted to see whether the error still occurs.

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