CXSMW Command — SMS White List

Enables or disables incoming SMS filtering through a whitelist of authorized phone numbers.

What is it for?

🔐 Main use cases:

🛡️ Protect device against unauthorized SMS commands
📱 Restrict control to specific numbers
🏢 Centralized fleet control
🔒 Security in production environments

When the White List is enabled, only SMS from numbers registered in destinations SM0-SM4 will be processed.

Features

Feature	Value
States	`0` = Disabled, `1` = Enabled
Number list	SM0 - SM4 (5 numbers maximum)
Persistence	NVS (survives reboots)
Available since	Firmware v1.9.08

Commands

Operation	Syntax	Description
Configure	`SCXSMWE`	Enables/disables White List
Query	`SCXSMW`	Reads current state
Response	`RCXSMWE`	Confirmation with state

Parameters

Parameter	Description	Values
`E`	White List state	`0` = Disabled, `1` = Enabled

Examples

Enable White List


>SCXSMW1<
// Response: RCXSMW1
// Device will only accept SMS from numbers in SM0-SM4

Disable White List


>SCXSMW0<
// Response: RCXSMW0
// Device will accept SMS from any number

Query state


>SCXSMW<
// Response: RCXSMW1 (enabled) or RCXSMW0 (disabled)

Authorized Numbers Configuration

The White List uses numbers configured in SMS destinations (SM0-SM4):


// Configure authorized numbers
>SSM0+5491112345678<    // Number 1: Monitoring center
>SSM1+5491187654321<    // Number 2: Supervisor
 
// Verify configuration
>QSM0<
// Response: RSM0+5491112345678
 
// Clear number (send empty)
>SSM2<
// Response: RSM2

Available indexes

Index	NVS Key	Recommended use
SM0	SMS0	Monitoring center
SM1	SMS1	Main supervisor
SM2	SMS2	Secondary supervisor
SM3	SMS3	Emergency
SM4	SMS4	Backup

Internal Operation

When an SMS arrives and the White List is enabled:

QPW Exception: If the SMS doesn’t come from an authorized number but the first command is >QPW... (password), the SMS will still be processed. This allows access recovery in case of losing authorized numbers.

Partial matching

Validation uses substring search (strstr), allowing partial matches:

Number in SM0	SMS from	Result
`12345678`	`+5491112345678`	✅ MATCH
`12345678`	`+5491198765432`	❌ NO MATCH

It’s recommended to use complete international format with country code for better precision and avoid false positives.

Use Cases

Fleet with centralized control


// 1. Configure monitoring center number
>SSM0+5491140001234<
 
// 2. Configure supervisor number
>SSM1+5491140005678<
 
// 3. Enable White List
>SCXSMW1<
 
// Result: Only the center and supervisor can send SMS commands

Temporarily disable for diagnostics


// Disable for testing
>SCXSMW0<
 
// Perform tests from any number...
 
// Re-enable
>SCXSMW1<

Verify complete configuration


// Verify White List state
>SCXSMW<
// Response: RCXSMW1
 
// Verify authorized numbers
>QSM0<
// Response: RSM0+5491140001234
 
>QSM1<
// Response: RSM1+5491140005678
 
>QSM2<
// Response: RSM2 (empty)

Security Considerations

Recommendations

Recommendation	Description
✅ Enable in production	Protects against unauthorized SMS commands
✅ Use international format	Include country code to avoid false positives
✅ Verify numbers	Before enabling, confirm SM0-SM4
✅ Configuration backup	Numbers are stored in NVS

Potential risks

Risk	Mitigation
Empty White List	No SMS will be processed if enabled without numbers
Incorrect numbers	Verify with `QSM` before enabling
False partial match	Use complete numbers with country code

Important! If you enable the White List without configured numbers, no SMS will be processed.

Troubleshooting

Problem	Probable cause	Solution
SMS not processed	White List enabled without numbers	Add numbers to SM0-SM4 or disable with `>SCXSMW0<`
SMS ignored from known number	Different number format	Verify exact format with `>QSMx<`
Responses don’t arrive	Incorrect SMS destination	Configure SM0-SM4 correctly

Compatibility

💾Firmware:v1.9.08

SP-IOT

SM-IOT

ZE-IOT