If wireshark shows nothing, and your blocking recv blocks, and your non-blocking recv shows nothing then there can only be one conclusion:
The data is not arriving at the machine you are expecting it to.
Find out why (hardware firewalling/routers elsewhere?). Wireshark gets its data from the raw network device, so locally present iptables are not in effect.

In reply to Re: How to use STUN? And other UDP-related problems. by Neighbour
in thread How to use STUN? And other UDP-related problems. by aitap

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