Good morning, 

I try to communicate to a router by sending http request. For this I use the FB LHTTP_PostPut from Siemens. I try 2 different actions : api/login and api/messages/actions/send. At the first attempt for 1 http request, it works, I receive a response code of 200 in the LHTTP_PostPut (that means the request was processed successfully), and the output done is true. The message from the router is store in a array “reponseData”.  I receive this first message correctly. After when I send a second http request the Fb LHTTP_PostPut  returns me an error 8641 with subfunction  8383. 

16#8641 Error of subordinate command MOV_BLK_VARIANT in region "TE_CHUNKED". The error code of the command is output to "diagnostics.subfunctionStatus". For the meaning of the respective error code, refer to the TIA Portal information system.

16#8383 The value at the SRC_INDEX is outside the high limit of the ARRAY.

The strange thing is I still receive the response code of 200, but the message from the router can not reach my Siemens PLC. Each time I turn off and turn on the Siemens PLC, the first request is working but the following ones, no. For the request api/messages/actions/send, the router sends a SMS. Even If I dont receive a message from the LHTTP_PostPut, the SMS is sent by the router, for the second request and more . 
 

I tried to find the solution on the forum, youtube, chatGPT, but no "solution" is working. 

I changed the parameter of the LHTTP_PostPut  , put the keepConnection to False and to True, 

I tried to change the user Field (header of the http request): by putting ‘Accept-Encoding: identity$R$LConnection: close$R$L$00’ .
I tried to increase the size of the different arrays of the input of the LHTTP_PostPut.

But no success until now :(

 If you have any ideas, it will help me a lot.

Thank you in advance for your time. :)

Link for the  FB LHTTP_PostPut from : https://support.industry.siemens.com/cs/de/en/view/109780503

Link for the Move_Blk_variant: https://support.industry.siemens.com/cs/de/de/view/109747174/96821112587