Is it possible to use Wi-Fi as a wireless connection to my Arduino/Windows PC LAN without using the internet My Situation and Problem:

I am wanting to put together a system to help monitor the soil moisture content in my garden and a small heated greenhouse I use in the winter. Also, In the near future I would like to build a system to remotely monitor the nutrients in my soil and other grow media, and have it accessible through my computer using a system similar to the one I'll have monitoring the moisture levels. In both situations I am growing nearly all crops hydroponically.

I have found several instances of people doing this by having the information posted to a service provider's website. Then it is possible to access the information by way of email or connecting in some manner to the service provider's site.

I plan to store the data in the cloud, but where I live we get internet access through satellite dish or land based re-transmission sites. So, I am planning to keep all gathered data in "The Cloud" manually, once received when I turn on my computer. I even have to use a booster device in my house to get dependable cell phone service. My land line telephone service provider doesn't offer high speed internet service, so I don't presently use a smart phone. I recently read a news article talking about a similar, though more widespread situation in Australia. In Australia they call it the tyranny of distance.

In addition to my garden and greenhouse, I have several other ideas for using Arduino to gather data using wifi and do any number of other things, and most of these ideas include accessing the gathered data through my computer connected to an Arduino device as required. It would certainly be helpful if anyone would be willing to share any ideas or point me toward inexpensive solutions.

Thanks for your kind consideration.
I have a hydroponic setup working. Actually I'm working in a second version. My solution is this:



I'm using a nodeMCU, because it have WiFi and lots of memory. In the breadboard I also have a real time clock (RTC), a LDR to measure real light level, and a temp/humidity sensor (DH-11), plus a small OLED display. The green led represent the HID light for testing purposes. I still need to add more elements, but it's good enough to show you my setup.

The nodeMCU send information to a MQTT broker . I can watch that information using an MQTT client in my Android smartphone. With the same client I can send orders to the nodeMCU (like changing light schedule, etc.)

MQTT is a protocol designed for Internet of Thing. It small and simple. You need a broker (server) to receive and send messages. I'm using Mosquitto running on Linux, on a old laptop that is on all time.

This is the big picture (no Internet involved):



Mosquitto is free, and it's available for PC, Mac and Linux here.

You have free clients for Android, iPhone, Windows, Mac, and Chrome. I'm using MQTT Dash.

MQTT is lightweight, easy, multiplatform, multiclient, and the best part of it: minimal programming.