Most of all devices support commands. They used for device configuration, changing state or request information. Commands can be sent via same internet connection used to post data from device to server or via SMS, mostly both. Traccar has native command support for limited number of protocols, but if user knows command format he can sent "Custom command" for any device. Custom command must be in HEX for binary protocol and string for string protocol.
SMPP server must be configured to send command via SMS, and device have to have Phone field set according number plan, ref. Notifications.
Command answer or command execution result also supported for limited number of protocols, if it is received and decoded appropriate Event will be risen.
In case command is sent via internet and device in not online it will be queued. All commands from device queue will be sent as soon as the device become online again.
It is not recommended to put a lot of commands in queue, because some devices ignore next command until they handle previous.
Sometimes user need to sent the same set of commands frequently. "Saved commands" help with routine.
User can create "Saved command" with desired parameters ...
... link it to a device or to a group ...
... and quickly select it from list in "Send command" dialog.
Also there is a "Limit commands" user permission to forbid user send not "Saved commands", in other words, user won't be able send any command except "Saved commands" he has access. User with "Limit Commands" can't create new "Saved commands" but only send predefined by manager or administrator.