Why can not I read bytes from the TcpClient in C#?

Question

Why can not I read bytes from the TcpClient in C#?

Here is the error I am getting:

Unable to read data from the transport connection: An established connection was aborted by the software in your host machine.

Here is how I start my TcpClient:

    public static async void Start()
    {
        TcpListener server = null;
        try
        {
            server = new TcpListener(IPAddress.Loopback, 13000);
            server.Start();

            var client = await server.AcceptTcpClientAsync();

            var stream = client.GetStream();
            var bytes = Convert.FromBase64String("ABCD");
            await stream.WriteAsync(bytes, 0, bytes.Length);

            client.Close();
        }
        catch (Exception e)
        {
            throw;
        }
        finally
        {
            if(server != null)
            {
                server.Stop();
            }
        }
    }

Here is how I run a request to the TcpClient:

try {
    var response = (new HttpClient()).GetByteArrayAsync("http://localhost:13000").Result;
    return Convert.ToBase64String(response);
} catch(Exception e) {
    throw;
}

The return Convert.ToBase64String(response); line is never reached. While I see the quoted above error message inside the Exception e if I hit a breakpoint on the throw line.

Also, during debug the Start() method completes just fine. I.e. it starts, then wait for a request, gets a request, writes to the TclClient and at the end runs the server.Stop(); command.

I am expecting my code to work, because I took it and modified from the official documentation over here.

I tried to check out a few resources which would tackle my exception, but none of them did help.

E.g. I tried to use the question.

First answer tells nothing useful actually, but just plays around with words and at the end states that one can do nothing about the exception (please, correct me if I am missing a point in the answer).

And the second answer tells an impossible in my case problem. Because, I am sure there is nothing running on the 13000 port.

Answer 1

Your client code is using HttpClient, which sends an HTTP request and expects an HTTP response. But your server is not an HTTP server, it is just a plain TCP server, so the client is likely to fail and forcibly close the connection when it doesn't receive a properly formatted HTTP response.

The "official documentation" whose example you modified is not using HttpClient at all, it is using TcpClient instead.

If you want to use HttpClient in your client, then you should use HttpListener instead of TcpListener in your server.