How can wireless networks send messages for free?

First of all, we should understand that short message service is a service mode that uses control channel to transmit a small amount of data information. It is completely different from data channel or wireless network and needs a special gateway to connect with each other.

Secondly, the sending and receiving of short messages need the network node of short message server, and the gateway to this server in other networks is usually called short message gateway.

Thirdly, the interface of SMS gateway is controlled by the operator, and only SP (service provider) recognized by the operator can use it.

So it can be seen that whether you can send text messages for free depends entirely on which SP you use and whether he sends them to you for free.

For example, the 139 mailbox will give 30 short messages to mobile phone users every month, so that users can visit the 139 mailbox and send 30 free short messages when surfing the Internet wirelessly.