What is the reason for Bluetooth not connecting?

Reasons for Bluetooth not connecting: not in pairing mode, low battery, incompatible Bluetooth versions.

1, did not enter the pairing mode

Bluetooth headset and other devices to connect, you need to enter the pairing mode, this is the Bluetooth device's security mechanism, in the case of not entering the pairing mode, the other devices can not be found in the Bluetooth headset.

When the Bluetooth headset enters pairing mode, you need to press and hold the power button for 3 to 5 seconds under the power off state, when the headset indicator light flashes alternately, you can find the Bluetooth headset on other devices, and then click the name of the headset to complete the pairing.

2, low battery

Bluetooth headsets usually rely on the built-in battery to keep them working, and when the headset's battery is low, pressing the button to enter pairing mode may automatically shut down the headset because of the low battery, resulting in interrupted pairing. You should charge your Bluetooth headset first, and then connect it to your Bluetooth headset when it's fully charged, to solve the problem.

3, Bluetooth version is not compatible

Bluetooth is a communication protocol, if the Bluetooth headset supported by the Bluetooth protocol version is not compatible with other devices, the same will lead to connection failure. Check your device's Bluetooth version, and if it's not compatible, try a device with the same protocol to troubleshoot the headset's hardware.

The main problems with Bluetooth are as follows:

(1) Bluetooth's power consumption. Bluetooth transmits data infrequently and consumes less energy in the process of transmitting data, however, polling access during the waiting process in order to respond to connection requests in a timely manner is very energy intensive.

(2) The connection process of Bluetooth is cumbersome. Bluetooth's connection process involves multiple information transfer and verification processes, which on the surface does not seem to allow users to feel the complexity of the connection process, but the repeated data encryption and decryption processes and the authentication process required for each connection is a great waste of computing resources for the device.

(3) Security of Bluetooth. The first pairing of Bluetooth requires the user to verify the PIN code, which is generally composed of numbers only, and the number of digits is very small, generally 4 to 6. After the generation of the PIN code, the device will automatically use Bluetooth's own E2 or E3 encryption algorithms to encrypt the PIN code, and then transmit the identity of the authentication.

In this process, hackers are likely to intercept packets, connect disguised as the target Bluetooth device, or use brute-force attacks to crack the PIN code. In addition, the security of the encryption algorithms used in the process of transmitting data over Bluetooth needs to be improved. The reason for the above situation lies in the Bluetooth technology itself.

Because the design goal of Bluetooth is to form a base-less LAN (similar to WLAN's AdHoc mode) between devices for close-range communication between multiple devices, the Bluetooth protocol requires authentication before each connection in order to ensure privacy and security.