Reconnecting.Error Code HCNetSDK.dll[91] (solved)

If you are looking for a solution to fix the Error Code HCNetSDK.dll[91] on your Hikvision camera, don't look any further. Just read this article...

Hikvision Reconnecting Error Code 91

There are two main reasons to have this issue with your IP camera.

The Hikvision reconnecting Error Code HCNetSDK.dll[91] occurs when there's no enough power for the camera or when the Auto Change stream type is on. The easiest solution to solve the problem is to use a better PoE power supply and turn the auto change stream off.  

The problem with power

When using PoE (Power Over Ethernet) to power the camera up, is necessary to follow the international standards such as the IEEE 802.3af and IEEE 802.3at to have enough power.

IP camera using PoE

Each one these IEEE standards are designed to have specific voltage (V) and power (W) for the cameras and you need to use the correct power supply to have your camera working properly without some type of error. 

You can use either a PoE switch or a PoE power supply, just ask the vendor a model that follows the IEEE 802.3af standard for fix cameras (dome or bullet) or the IEEE 802.3at standard for PTZ cameras.

Some users and technicians have reported a problem with the message in the iVMS-4200 screen "Reconnecting.Error Code HCNetSDK.dll[91]" due to the lack of power for the camera (when using the wrong PoE power supply).

Just make sure you are using the correct PoE power supply or switch.

To learn more about PoE read the article PoE switch for IP camera

The auto change stream type 

The IP camera or recorder generates a different type of video stream such as main stream and sub stream to send through the network.

Those type of stream can vary according to the resolution, frame rate and compression (such as H.264, H.264+ and H.265) and when the camera changes the stream automatically that can cause some issues.

To prevent the Reconnecting.Error Code HCNetSDK.dll[91] error just open the iVMS-4200 to change the parameter (see the picture below).

Click Tools --> System Configuration

iVMS-4200 System configuration

Just uncheck the Auto-change Stream Type option in the Image Menu

Change the auto stream parameter

This simple change should do the job, now just come back to the main screen and reload the cameras and the error should go away.

Hikvision camera without the error

If some reason the cameras are still not loading properly just restart the iVMS-4500, sometimes a refresh can save the day.

Other factors to consider

If you follow the instruction above everything should work correctly, however, sometimes there are some details that can prevent your camera to work.

Let's see some extra procedures to help you get rid of the problem.

Infrastructure (cables)

Remember we talked about the use of the correct PoE switch or Power supply to power the camera up? 

Guess what... they send power through cables ! 

If you are not using good quality cables the power or data can be compromised and your system can fail and sometimes even generate the same "Reconnecting.Error Code HCNetSDK.dll[91]"  error.

For IP camera is recommended to use cat5e or cat 6 UTP cables.

UTP cable

Also, make sure the cable are from a good manufacturer such as Furukawa or another brand that is reliable.

You also have to take the distance into consideration, the limitation for UTP cable for data transmission is 100m according to the international standard.

Camera factory default reset

Sometimes a bad configuration or a corrupted configuration file can hold your camera in an error state, so it's a good practice to reset the device to factory default and reconfigure it from scratch.

Just login into the camera, go to the Upgrade & Maintenance menu.

Click the restore button (see the picture below).

Hikvision DVR factory default

After restoring the camera to factory default configure it manually (don't import a file with the old configuration).

Firmware upgrade

It's important to keep all the devices with the last firmware to make sure everything works fine, so take a look at the manufacturer website to see if there's a new firmware for your device.

You can also go directly to your device menu and click the button to check for the last firmware available.

Hikvision DVR check for new firmware


The Reconnecting.Error Code HCNetSDK.dll[91]" can be eliminated by following the instructions in this article, just make sure to execute each step and if some reason the problem still remains call the Hikvision support.

I hope this article can help you to solve your problem.

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