So, if you already have verified that your server program does see the correct data, why are you still posting both halves of the application? Or did you not verify that your server program gets the correct data?

If you already know that your server program receives data, why did you not hardcode the received data and checked it? Eliminating the client from the problem helps reduce the number of points of failure.

I recommend you use CGI to parse your query data in the server program. If you are using hand-rolled code to parse the query data, please eliminate that in favor of CGI or another query parser module. You should be aware that there are multiple ways to pass query data in POST requests, and I already told you that your way of passing it is different from other ways. CGI can handle both ways, but it's unclear whether your unshown code can handle them