Failed to connect to the remote server from WinRT

I am making an application that basically just needs to send a piece of XML to the server and return. I am having problems, however, in order for this to work and get very strange errors.

public bool Post(string data)
    {
        string server="http://my-lan-computer:9091/foo"
        bool success = false;
        HttpClient client = new HttpClient();

        try
        {
            client.PostAsync(server, new StringContent(data, Encoding.UTF8, "text/xml")).Wait(); //error here
            success = true;
        } catch { }

        return success;

    }

The server I am sending the message to is not localhost, but it is a computer on my local network. I get this error deeply nested:

innerException: {"An error occurred while sending the request."}

innerException: {"Unable to connect to the remote server"}

innerException: {"An attempt was made to access a socket in a way forbidden by its access permissions 123.123.123.123:9091"}

I have the option of an internet client in my application. I can access my local network and the Internet with other store apps. I can access the resource in firefox to get the correct behavior. I do not have a firewall or antivirus that would block these ports

What can cause this unclear error? How can i fix this?