As others commented, there are different ways to do this. If you are going for http server, perhaps you want to make GET or POST API so that the client (Processing) makes an API call (optionally send data) and the server (ESP32) returns the data.
(I couldn’t find an example for Processing + ESP32)
However, as Richard wrote, using UDP is another direction and this may be easier to understand the data flow. Since you are making a greenhouse, I assume that you don’t have to send data every 10 milliseconds, so either HTTP or UDP would be fine in your use case. My recommendation is, if you don’t have much time, UDP would give a quicker solution, and if you want to invest time and make the system efficient and scalable, HTTP would suit you better.