Problem with Remote Domoticz

[Kedi]

I have a remote Domoticz, which sends 8 devices to the main Domoticz. It looks like all tose devices are received by the master in good order.
The last few weeks I get errors like "RemoteDomoticz: Invalid data received" with no extra info.
I added some info about the data in the Source and compiled it again. No I receive this data.

Code: Select all

2026-04-06 12:36:27.803  Error: RemoteDomoticz: Invalid data received: {"BatteryLevel":100,"Color":"","
2026-04-06 12:36:27.803  Error: RemoteDomoticz: Invalid data received: ʘ�gSӫ՚켥ҒΪœp	дמȎʨ{
2026-04-06 12:36:27.805  Error: RemoteDomoticz: Invalid data received: zT\Ϻ�ڲ˴㡢۹ѾgȟAuK�JFݷI熢V[ɣFЯӟͱB˯ü텖勮˭x�zWkǥ?fT򡦢19�	ӂֶ>10iQS�Qʄ9:ڷVӞL䲡К`u�ݱ3(ӧb𣙓�

Anybody any idea where to look for or how logging could be enhanced or what is going on?

[gizmocuz]

I have a remote Domoticz, which sends 8 devices to the main Domoticz. It looks like all tose devices are received by the master in good order.
The last few weeks I get errors like "RemoteDomoticz: Invalid data received" with no extra info.

Thanks for reporting. I assume you made a patch in DomoticzTCP::OnData

Root Cause

TCP is a stream protocol — there is no guarantee that one async_read_some call delivers exactly one complete message. When devices update rapidly (the user has 8 devices), two problems occur:

- 1. Fragmentation: A large encrypted payload arrives in multiple TCP segments → OnData gets a partial ciphertext → AES decrypt fails
- 2. Coalescing: Multiple device updates sent back-to-back arrive as one blob → only the first message (if it decrypts at all) is processed

Neither the server (tcpserver/TCPServer.cpp → SendToClient) nor the client (hardware/DomoticzTCP.cpp → OnData) use any length prefix or reassembly buffer. The raw encrypted bytes are passed directly to AESDecryptData regardless of completeness.

I increased the server/client version number, and a length field. This should now be solved in the latest beta version (17667).
Do note that you need to upgrade both instances

[Kedi]

Tnx, for the response and the solution.
Unfortunately the remote cannot be directly updated, do that perhaps in a few days.
Sometimes the first message is a little longer, like
RemoteDomoticz: Invalid data received: {"BatteryLevel":100,"Color":"","DeviceID":"42244","LastLevel":0,"LastUpdate":"2026-04-08 14:06:24","Name":"Badkamer.","Options":"","OrgDeviceRowID":146,"OrgHardwareID":7,"Signa

B.t.w. the DeviceID 42244 does not exists on both sides???

[gizmocuz]

If you made the patch in DomoticzTCP::OnData, after it tries to parse the JSON, It means the decryption did not went correct.

I think it is because of a truncation issue.

I made some more changes that should also catch this issue in beta 17676 (using it myself with 4 instances)

[Kedi]

It took some time, because I had to go on a holliday for 2 months.
I upgraded both master and remote to build 18063 and everything is working now as it should.
Tnx. for the fix.