Make a post request through a tcp connection in c#

Question

I am asking this question primarily to learn. First I tried to make a regular post request and I got this error: C#: Handling WebClient "protocol violation". Then I tried to make a raw connection to understand what was going on and end up being curios.

Anyways here is my question:

I am using fiddler to capture the post request that I am trying to replicate. Here is how the request looks like when capturing it on fiddler:

Note on top I have the request and on the bottom I have the response. Also see how my response is 200 OK

Another proof that this is working is when I run this curl command: Note how I get a response.

Now I want to do the same thing with c# here is my code:

        // connect to device
        TcpClient client = new TcpClient();
        client.Connect(System.Net.IPAddress.Parse("170.55.7.163"), 80);

        // create post data to be sent
        string postDataAsString = @"POST http://170.55.7.163/cgi-bin/api.values.post HTTP/1.1" + Environment.NewLine +
            "Host: 170.55.7.163" + Environment.NewLine +
            "Content-Length: 25" + Environment.NewLine +
            Environment.NewLine +
            Environment.NewLine +
            "P270=2&sid=3dc7588be24f";

        byte[] postDataBinary = System.Text.Encoding.UTF8.GetBytes(postDataAsString);

        // make post request
        client.Client.Send(postDataBinary);

        // get response
        byte[] bytes = new byte[1024];
        int lengthOfResponse = client.Client.Receive(bytes);

        var resp = System.Text.Encoding.UTF8.GetString(bytes, 0, lengthOfResponse);

        // I get a bad request in here why!? 

I do not get a 200 response why? What can I be doing wrong :/ . I will like to learn what I am doing wrong.

Answer 1

After wasting 4 hours of being so curios I found the problem. I changed:

string postDataAsString = @"POST http://170.55.7.163/cgi-bin/api.values.post HTTP/1.1" + Environment.NewLine +
        "Host: 170.55.7.163" + Environment.NewLine +
        "Content-Length: 25" + Environment.NewLine +
        Environment.NewLine +
        Environment.NewLine +
        "P270=2&sid=3dc7588be24f";

TO

string postDataAsString = @"POST /cgi-bin/api.values.post HTTP/1.1" + Environment.NewLine +
            "Host: 170.55.7.163" + Environment.NewLine +
            "Content-Length: 25" + Environment.NewLine +
            Environment.NewLine +
            Environment.NewLine +
            "P270=2&sid=6aec588bfe62";

Removing http://170.55.7.163 from the first line fixed the problem. I think there was nothing wrong with the code the problem is the http server running on 170.55.7.163.