Why is Microsoft-windows-security-auditing blocking my app. ?

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VB

Hi,

I'm having a problem with a project using TCP communications between Windows 10 and Windows 7 laptops. Both on the same LAN.

I have EXACTLY the same application in both machines, initiating the WiFi connection between the two machines using the Win.10 the connection is made almost immediately but the other way round doesn't connect at all.
Both machines have Microsoft Security Essentials as their AV protection.

The firewalls in both machines are supposed to accept the app. (Publicly and Privately), however when I check the Windows Security Log for the Win.10 machine, (seconds after a comm's failure) I find the following entry:

Quote:

Log Name: Security
Source: Microsoft-Windows-Security-Auditing
Date: 29/04/19 01:06:25
Event ID: 5032
Task Category: Other System Events
Level: Information
Keywords: Audit Failure
User: N/A
Computer: MSI
Description:
Windows Firewall was unable to notify the user that it blocked an application from accepting incoming connections on the network.

Error Code: 5
Event Xml:
<event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<system>
<provider name="Microsoft-Windows-Security-Auditing" guid="{54849625-5478-4994-a5ba-3e3b0328c30d}">
<eventid>5032
<version>0
<level>0
<task>12292
<opcode>0
<keywords>0x8010000000000000
<timecreated systemtime="2019-04-29T00:06:25.742620500Z">
<eventrecordid>104834
<correlation activityid="{397352cc-fdbb-0003-d452-7339bbfdd401}">
<execution processid="876" threadid="7680">
<channel>Security
<computer>MSI
<security>

<eventdata>
5

I don't understand much of this, but it seems to be saying it's blocking the app. that is specifically listed as 'Allow'.

Microsoft say that error 5 means:

Quote:

This article describes the symptoms, cause and resolution steps for situations where AD operations fail with error 5: Access is denied.

DCDIAG reports that Active Directory Replications test has failed with error status code (5): "access is denied"
Testing server: <site name="">\<destination dc="" name="">
Starting test: Replications
* Replications Check
[Replications Check,<destination dc="" name]="" a="" recent="" replication="" attempt="" failed:
from="" <source=""> to <destination dc="">
Naming Context: <directory partition="" dn="" path="">
The replication generated an error (5):
Access is denied.
The failure occurred at <date> .
The last success occurred at <date> .
3 failures have occurred since the last success.

I have no idea what that means...

I'm using VB.NET with VS 2017 although I don't believe that's relevant.

What I have tried:

I have the same code in both machines, I have the same AV in both machines, Win.7 accepts WiFi connection from Win.10, Win.10 blocks Win.7. I'm just trying to make a little 'Two computer game' to be played between two computers on the same LAN so I don't want to have to start messing with individual firewalls, I just want to be able to install the executable code in each (any windows) machine and play the game.