Hi Amar,
this error basically means that the receiver system interrupts the connection.
If you say so that this error happens only if the size of the message is too large than please check the ICM parameter icm/HTTP/max_request_size_KB value on the receiver system side. But it is advised to check this on the PI system too...
If this parameter is big enough to handle the request size you send from PI, than also check the other ICM parameters as well:
824554 - ICM and SAP Web Dispatcher timeout parameters
Best Regards,
Viktor