The "server has shut down the connection prematurely" message is
referring to the TCP connection between de load generator and the
server.
It means that a TCP reset packet has been received and is a means to
abort or refuse a TCP connection (it could also be send by e.g a
firewall or HIPS in the network path).
Thus it is usually an indication that something is wrong / overloaded
at the server.
The web_set_sockets_option() allows you to ignore this, hence no more
error messages.
By the way, MS Internet Explorer is notorious for aborting TCP
connections this way (client side). If you want your script to behave
this way too you have to use web_set_sockets_option("SHUTDOWN_MODE",
"ABRUPT");
André