What causes this error?
Could be a few things any extra detail you can provide would be helpful. Generally this error means the pipeline went down between client and commserve.
That could make sense, I'm using the app across the WAN.
What you can do to see if the link is dropping is try created a subclient with a small amount of data and see if it completes. You may also want to reduce the number of readers to reduce the network usage.
For WAN link tuning the network agent may allow a more reliable connection if set to 1.