Question

EDIT: Removed code/explanation because this project has been given again and students can easily find the solution via this post.

To clarify what happened, I simply passed the wrong length/size in my recvfrom() call.

Answer 1

In this line:

if(recvfrom( temp->sockfd, sendHostIP, BUFFER_LEN, 0, (struct sockaddr *)&recvAddr, &recvLen) < 0)
    errorMsg("recvfrom");

You pass BUFFER_LEN as the length (256), but sendHostIP is only of length MAXHOSTNAMELEN (64).

This causes recvfrom() to overflow that buffer. The same problem occurs when you read in to localHostIP.