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By schufti
#66795 if you go to ebay and look for "nodemcu" or "wemos D1" you will find similar devices for less.
They are good for development but for samples or series you would like to look for something simpler like ESP-01 if you want to go for battery powered (enough threads on this topic).

depending on the availability of (free) wifi you might have to consider various scenarios.
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By Blikin
#67246 Thanks for your answers, Folks. I hadn't seen them, because unlike most forums, default bahaviour of this one does not send an email notification that a thread has been answered. I'll check to see if I can change a setting to make it do so.
I have bought 5 NodeMCU boards from Ebay, and I've signed up to an IoT course through Instructables, so I'm ready to go. Just looking around for a few basic items first.
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By Blikin
#67773 Since my original post on this thread, I have followed a course on "Instructables", and have been able to wire a button and a LED to a NodeMCU, and have it send notification that the button was pressed to website AdafruitIO (AIO), and to have IFTTT detect the trigger on AIO and send a) an email, and b) a command back to the NodeMCU to tell it to light the LED.
So, I have made a start, but I still have a long way to go to accomplish the project outlined at the top of this thread.
I don't mind using Lua or AT commands, but the NodeMCUs will now be installed in four houses along the same side of the road. Let's call them A,B,C,D. The wireless signal will have to penetrate walls, so house A will not be able to communicate with D, but adjacent houses should be OK. I favour a P2P network, as each node, if triggered, will alert a neighbour, but if no help arrives within a few minutes, it will call other houses by using intermediate nodes, then finally use the WiFi router in the house that caused the alert to signal a family member by SMS.
Although I am a retired computer engineer, my networking experience has all been on mainframe channels and computer centre LANs like FDDI, Fibre Channel, SCSI, HIPPI, etc - I have very limited knowledge of WiFi or Internetworking, so I need quite a lot of pretty basic information to get me going. I'm really depending on pointers from people like you, who know the subject much better than I do. I have also downloaded three books on Lua, so I have some reading to do.
I do not intend to commercialise the product, so when it is complete, I will write it up and make it available to all.
My immediate questions concern setting up a P2P network between several (up to 6) NodeMCU boards. Can anybody give me links or help me out?
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By alex_g
#67810 Do I understand correctly that
1) These houses (being oldies) have no WiFi?
2) Two ESP8266s might be able to communicate between adjacent houses, but not all of them can do so between themselves?

If so, you're probably making a rod for your back, and it might be easier to use some sort of hard-wired solution. I'm not sure what p2p network you could make with constraints 1) and 2), but it sounds quite difficult - and probably beyond the scope of simple ESP8266 programming - as you'd need to have some sort of relay system going, with the ESPs working both as stations and APs.

Not saying it can't be done, but you'd sure have to get pretty good at "WiFi and internetworking" as you put it. Could take months.

OTOH, if the houses do have WiFi routers, then MQTT is probably the easiest way to approach this, as it's practically tailor-made for that sort of application.