What is error 10038? And, why does it occur upon termination of the DHCP Server?

In the trace file (dhcptrc.txt) you will see the follwing trace entries:

[11/07/2012 07:07:07] DHCP Server is terminating (ignore error messages that follow)
[11/07/2012 07:07:07] recvfrom returns with error 10038

This happens every time you terminate the DHCP server. The reason is of technical nature and is by design. There is nothing to worry about, because it is intended behavior.
The reason for it lies in the fact that the DHCP Server software uses blocking sockets as a communication resource. The DHCP Server basically is blocked in a socket call and waits for a request from a client. When you terminate the DHCP Server application, then the blocking socket function call is de-blocked by closing the socket. This then leads to the error message 10038.