Commands
Commands can be sent by data or SMS, so you don't need SMS to send commands. Note that commands over data connection can only be sent when device is online.
Device online? When gps sends data to server? Or anytime gps still "connected" to traccar server? If only when tracker sends location, does traccar have queue for submitted commands?
Online means that there is an active TCP connection between server and the device. Traccar doesn't queue commands.
Good Day
Just a question: are commands send by sms or by data or both?
Does my server need sms functionality to send commands to trackers?