#16054 "action - rpc call request" rule node failing to send WriteReplace message to a LwM2M unsigned int resource · thingsboard

Describe the bug An "action rpc call request" rule node returns "BAD_REQUEST" error after a request to update an UNSIGNED INTEGER LwM2M resource with an unsigned value. Using wireshark I can confirm the message is never issued from Thingsboard server to device.

My Server Environment

own setup
- Deployment: monolith
- Deployment type: rpm on an AWS EC2 instance
- ThingsBoard Version 4.2.0
- Community Edition
- OS Name and Version: Amazon Linux 2023, Version 2023.10.20260105

My Device Device firmware built on a STM32L4P5 MCU using a cellular 4G modem implementing a LwM2M version 1.1 client (based on Wakaama library)

My Client Workstation

OS: Windows 11
Browser: Microsoft Edge
Version: 151.0.4129.101

To Reproduce I am showing the rule chain piece allowing to reproduce the behavior:

Explanation: Node #1: a RPC call request reading resource /38031/0/7 is read from device. Message payload: { "method": "Read", "params": { "id": "/38031/0/7" }. Message type: RPC_CALL_FROM_SERVER_TO_DEVICE. Resource /38031/0/7 contains a hash of current device's configuration.

Node #2: a switch filter node comparing device's configuration hash coming from node #1 against server stored configuration hash for that device. If both do match, next action routed via the "AlreadyInSync" path; otherwise the next action/node is routed via the "HashMismatch" path.

Node #3: a transformation-script node in charge of parsing the message to be sent to the device to update its configuration (stored at device's resource /38031/0/1, defined as an 32-bit unsigned integer). The script implemented in node #3 is the following:

var portMask = JSON.parse(metadata.ss_portInputMask);
var maskInt = 0;
for (var i = 0; i < portMask.size(); i++) {
    if (portMask[i] == true) {
        maskInt = maskInt | (1 << i);
    }
}
// use an unsigned zero-fill right shift in TBEL to force a 32-bit unsigned integer
var maskUnsigned = maskInt >>> 0;
var msg = {
    "method": "WriteReplace",
    "params": {
        "id": "/38031/0/1",
        "value": maskUnsigned
    }
};
return { msg: msg, metadata: metadata, msgType: "RPC_CALL_FROM_SERVER_TO_DEVICE" };

Node #4: an "action - rpc call request" rule node in charge of sending parsed message in previous node and send it back to device.

See below the simulation results by debugging node #4:

Image with captured events:

Detail of "Data" and "Metadata" message contents:

INPUT MSG

Event time: 2026-08-23 10:08:34.463

Data: { "method": "WriteReplace", "params": { "id": "/38031/0/1", "value": 13 } }

Metadata: { "deviceLabel": "Develop device", "deviceName": "867255079904415", "deviceType": "LwM2M_device_profile", "expirationTime": "1787472566290", "scope": "SERVER_SCOPE", "ss_active": "true", "ss_configurationChanged": "true", "ss_portInputMask": "[true,false,true,true,false,false,false,false,false,false,false,false]", "ss_processingRules": "[{"ruleID":0,"ruleName":"REGLA_0","rulePyld":[0,1,2,3,4,5,6,7,8,9,10,11,12]}, {"ruleID":1,"ruleName":"REGLA_1","rulePyld":[0,0,0,0,1,1,1,1,2,2,2,2,3]}]", "ss_ruleAlarmMask": " [false,true,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false]" }

OUPUT MSG #1

Event time: 2026-08-23 10:08:34.463

Data: { "method": "WriteReplace", "params": { "id": "/38031/0/1", "value": 13 } }

Metadata: { "deviceLabel": "Develop device", "deviceName": "867255079904415", "deviceType": "LwM2M_device_profile", "expirationTime": "1787472566290", "scope": "SERVER_SCOPE", "ss_active": "true", "ss_configurationChanged": "true", "ss_portInputMask": "[true,false,true,true,false,false,false,false,false,false,false,false]", "ss_processingRules": "[{"ruleID":0,"ruleName":"REGLA_0","rulePyld":[0,1,2,3,4,5,6,7,8,9,10,11,12]},{"ruleID":1,"ruleName":"REGLA_1","rulePyld":[0,0,0,0,1,1,1,1,2,2,2,2,3]}]", "ss_ruleAlarmMask": "[false,true,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false]" }

OUTPUT MSG #2

Event time: 2026-08-23 10:08:34.470

Data: { "result": "BAD_REQUEST", "error": "Resource id=/38031/0/1, value = 13, class = Integer. Format value is bad. Value for this Single Resource must be UNSIGNED_INTEGER!" }

Metadata: { "deviceLabel": "Develop device", "deviceName": "867255079904415", "deviceType": "LwM2M_device_profile", "expirationTime": "1787472566290", "scope": "SERVER_SCOPE", "ss_active": "true", "ss_configurationChanged": "true", "ss_portInputMask": "[true,false,true,true,false,false,false,false,false,false,false,false]", "ss_processingRules": "[{"ruleID":0,"ruleName":"REGLA_0","rulePyld":[0,1,2,3,4,5,6,7,8,9,10,11,12]},{"ruleID":1,"ruleName":"REGLA_1","rulePyld":[0,0,0,0,1,1,1,1,2,2,2,2,3]}]", "ss_ruleAlarmMask": "[false,true,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false]" }

Conclusion Output shown in output message #2 as "BAD_REQUEST" is not correct as value "13" is an unsigned integer. I tried to force the node #3 TBEL code ways to enforce unsigned integer for the "value" piece but in all cases the outcome is the same.

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