K-Link not working because of error 4002

28 August 2025 by

CTech Metrology, Luc Wens

these are the errors

Which kind off translates to

KLinkWinObserver::UnpackFaultEvent() Error

(KLINKWINOBSERVER_UNPACKFAULTEVENT)

KPublicTCPServer::Connect() Error

(KCOREPUBLICTCPSERVER_CONNECT)

KSingleTCPConnection::Activate() Error

(KSINGLETCPCONNECTION_ACTIVATE)

KSingleTCPConnection::ChangeState() Error

(KSINGLETCPCONNECTION_CHANGESTATE)

Undocumented error code

KSocketTCP::OpenServerSocket() Error

(KSOCKETTCP_OPENSERVERSOCKET)

Socket error

Permission to create a socket of the specified type and/or protocol is denied. For file sockets, search permission is denied for a component of the path prefix, or write permission is denied on the directory containing the directory entry. (K600_EACCES)

The big question is of course which port is giving the problems.

On the old DELL Tower it did work, and it did work on the new Dell as well, somewhere in the past, so my best guess is that some other program is blocking a port.

Used ports

Analysis of the source code gives this list:

#define KG2CAMERADRIVERPROTOCOL_CONFIGURATIONPORTNUMBER 10004
#define KG2CAMERADRIVERPROTOCOL_SERVERCONTROLPORTNUMBER 50030
#define KG2CAMERADRIVERPROTOCOL_SERVERDATAPORTNUMBER 50031
#define KLINK_NETWORK_CONFIGURATION_PORT 10002
#define KLINK_COMMANDPORT_ON_SERVER_TO_CLIENT 50020
#define KLINK_DATAPORT_ON_SERVER_TO_CLIENT 50021

.... digging into my good old blog gives this article https://ctechmetrology.blogspot.com/2022/08/k-link-does-not-start-due-to-ports.html#more

Old blog article

K-Link does not start due to ports being blocked

Sympton

When you start K-Link, it gives this error

Normal K-Link will work, but as soon as CTrack is installed it will stop since the TCP ports for KPI are no longer available.

Cause

Programs can block a range of TCP ports, this is typically by Hyper V, Docker or WSL

This can be checked with the next command

netsh int ipv4 show excludedportrange protocol=tcp

Giving the next result

Start Port End Port

---------- --------

2869 2869

5357 5357

10243 10243

49814 49913

50000 50059 *

50260 50359

50460 50559

50608 50707

50913 51012

51013 51112

51113 51212

51235 51334

62703 62802

62803 62902

* - Administered port exclusions.

As you can see the range 50000 to 50059 blocks port 50505 and 50506 which is used by KPI.

Solutions

Quick work around

As a quick work-around, you can type the next 2 commands

net stop winnat

net start winnat

If you type netsh again, you will see that the range is much smaller and the KPI port is available, now K-Link will work.

However, this needs to be done after each restart, so not a final solution.

Solution 1 : working definitive solution

Or as an alternative keep hyper V but block the ports yourself

Expanding on the selected answer: if you have Hyper-V enabled, you can temporarily disable it during boot by using bcdedit:

bcdedit /Set {current} hypervisorlaunchtype off

Restart and exclude the necessary ports via:

netsh int ipv4 add excludedportrange protocol=tcp startport=50505 numberofports=100

Then simply re-enable Hyper-V, then restart:

bcdedit /Set {current} hypervisorlaunchtype auto

This prevents having to completely remove and re-add the Hyper-V feature, which requires several restarts.

Solution 2

A more definitive solution is to get rid of Hyper V all together

Note: Run the following commands in powershell (Run as administrator)

Disable Hyper-V.
dism.exe /Online /Disable-Feature:Microsoft-Hyper-V
Remove all hyper-v related network adapters.
Get-HNSNetwork | Remove-HNSNetwork
Reboot.

Solution 3

Block the ports yourself with

netsh int ipv[46] set dynamic tcp start=49152 num=16384

Optionally disable the blocking of range of ports by
reg add HKLM\SYSTEM\CurrentControlSet\Services\hns\State /v EnableExcludedPortRange /d 0 /f