To start with I have to say I have seen few similar questions but none of those could help me with resolving my problem.

My setup is, two raspberry Pi 3 B+ with Raspberian on board(updated). One of them set up as hotspot with the use of hostapd and the other one connecting to it. Hotspot Raspberry is also connected to the router by the ethernet cable (eth0). I used following tutorial for the hotspot creation: https://thepi.io/how-to-use-your-raspberry-pi-as-a-wireless-access-point/

Purpose of this setup is to send from client raspberry data to the hotspot raspberry with the use of UDP. However there comes a problem.

It is possible to send data from client to hotspot but hotspot trying to communicate back to the client cannot send UDP packets(they get lost somewhere in the middle, no error while sending). However when I unplug ethernet cable from the hotspot raspberry it starts working, UDP packets from hotspot get delivered to the client. When I plug it back again it stops working.

I'm not networking expert and I'm mostly guessing but there is some problem with that Internet bridge(between ethernet and wifi) interfering with UDP communication from hotspot to connected clients. Can you tell me what could be a problem and how could I solve it?

Edit: Is there maybe other way I could do that? Alternative could also be an option. However I would prefer to still kinda use wifi.

  • Your problem is probably the non-existent OS "Raspberian". You have provided NO evidence of problem or NO example of what you tried or how you configured your network so NO ONE can help. The tutorial you claim to have followed uses obsolete tools.
    – Milliways
    Commented Sep 4, 2019 at 7:36
  • I suppose you have a routing problem. But you are also asking for alternatives. So lets see if we can find one. You only want to transfer data from one RasPi to the other. You connect one RasPi to your internet router by wire. Does the second RasPi is also able to connect to the router by wire or wireless? Please address me with @Ingo, otherwise I won't see your reply.
    – Ingo
    Commented Sep 4, 2019 at 8:12
  • @Milliways What is currently used for creating a hotspot then? I was looking and found hostapd and thought it is pretty new. Evidence is using simple Python script and sending to hotspot and receiving data and not getting the same from the hotspot. How you want me to prove not receiving something besides timeout I get?
    – WakeCaine
    Commented Sep 6, 2019 at 8:28
  • @Ingo It seems to be the routing problem. I disabled static ips and they seem to get IP from a router instead of wifi hotspot. Which is strange and I wonder why. For demo we are doing I need internet and wifi hotspot that is a problem.
    – WakeCaine
    Commented Sep 6, 2019 at 8:34
  • Again my question: does the second RasPi is also able to connect to the router by wire or wireless? If so you don't need a hotspot to send data from one RasPi to the other. That was the question you asked.
    – Ingo
    Commented Sep 6, 2019 at 8:41


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