What do MT and MO mean?

MO= uplink, that is, the information sent by the user to SP. Uplink: mo submits a short message to the short message center; Downlink: mt SMS Center forwards SMS to specific users. Your message is like this. The SMS address you submitted is SMS Center. After receiving your message, the SMS center will store and forward it, and when forwarding, it will find a route to send it according to the number of the receiver you fill in. The same is true in the field of MMS. Downlink services: services initiated by SP, mainly referring to services initiated by SP to MMSC. Because the MMS center stores the forwarding, the MMS center forwards it to the receiver.