kannel is an open-source software that acts as a gateway for sending and receiving SMS messages. It is widely used by mobile network operators and businesses to facilitate communication through text messaging. Kannel supports various protocols, making it versatile for different applications. The software can connect to multiple SMS service providers and can handle a large volume of messages efficiently. Kannel is often used in conjunction with other systems, such as HTTP or SMPP, to enable seamless integration into existing applications and services, enhancing overall messaging capabilities.