socket write error when sending EDI document to TN URL


We are sending the EDI document to partner and able to receive the MDN from there URL. But when partner is sending the document to TN URL from there system they are receiving the following error:
Error(Error(com.cyclonecommerce.tradingengine.transport.UnableToProduceException: Software caused connection abort: socket write error

we have added partners URL to in our network firewall.

can you please have look and provide your comments.