Limit for receiving concurrent esp_now messages?

hdsjulian2
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Limit for receiving concurrent esp_now messages?

Postby hdsjulian2 » Wed Apr 09, 2025 1:06 pm

I have the following issue: i want to send an esp_now broadcast and then have every device on the network send a reply. Now my network has about 150 devices, so i am afraid that i'm going to DDOS the host.
Is there anyone here who has tested these kinds of things and maybe has an idea how many concurrent incoming esp_now messages an esp32 can handle? How does the system handle this? I'd greatly appreciate any insight...

MicroController
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Re: Limit for receiving concurrent esp_now messages?

Postby MicroController » Wed Apr 09, 2025 1:55 pm

The messages being sent on the same channel cannot actually be received concurrently, only in quick succession.

hdsjulian2
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Joined: Wed Apr 10, 2024 8:08 am

Re: Limit for receiving concurrent esp_now messages?

Postby hdsjulian2 » Wed Apr 09, 2025 11:17 pm

The messages being sent on the same channel cannot actually be received concurrently, only in quick succession.
Fair point. Now the question remains what would happen if you send a broadcast to 150 devices and they all, upon receipt, answer with a message to the sender. My guess is that there is going to be some microseconds variance in send / receive /respond times, still there might be a bunch of messages arriving at the same time, not being received, hence repeated. Then the question arises whether that will DDOS the system. Therefore i'm asking for experience before trying this out myself :)

Sprite
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Re: Limit for receiving concurrent esp_now messages?

Postby Sprite » Thu Apr 10, 2025 12:01 am

I think there will be a fair amount of traffic, but since ESP-Now uses standard WiFi management frames, they will still use carrier sense to make sure they don't talk over eachother. This means a bunch of small packets will arrive at the receiver at the same time. Because, again, ESP-Now uses the same hardware as WiFi and WiFi is optimized for doing things at a pretty high speed (to get a good throughput), I doubt 150 small packets is going to cause an issue.

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