I haven't seen the OP describe traffic originating from ports 53036, 53037, 53038, 53039.

Geez Louise. Re-read the OPs post but concentrate on a single pair of ports:

  1. The server listens on 4 ports 8020 ....
  2. The client sends the first heartbeat from ports: 53036, ... to ports 8020, ..., This repeats in every 10 seconds.
  3. When server ... [it] replies from ports 8020, ... to ports 53036, ....
  4. If ... the server ... sends them to ports 53036, ....

Graphically: 

step | Action | Server | direction | client 
-----+--------+--------+-----------+-------
 1   | Listen | 8020   |           |
-----+--------+--------+-----------+-------
 2   | h'beat | 8020   | <-------- | 53036  Client 53036 originates; S
+erver 8020 receives.
-----+--------+--------+-----------+-------
 3   | resp   | 8020   | --------> | 53036  Server 8020 originates; cl
+ient 53036 receives.
-----+--------+--------+-----------+-------
 4   | data   | 8020   | --------> | 53036  Server 8020 originates; cl
+ient 53036 receives. 
-----+--------+--------+-----------+-------

[download]

4 ports at the server, 4 ports at the client; 4 bi-directional conversations. There is no ambiguity.

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

The start of some sanity?

In reply to Re^8: UDP connection by BrowserUk
in thread UDP connection by falstad

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