Grab incoming images over LAN

I forget what it’s called, but there is an application that allows the user to see images being downloaded onto computers on the local network. Does anyone know the name?
Also There was a tool in high-school that my teacher showed us that you could connect to his device via wifi and go to a website, and the program would display all images from the page on his screen and also manipulate the images on each website ie. make them black and white or flip them when it sends it back to your device
Thanks!
Answer #1
Try Lan Detective: http://landetective.com/products/internet-monitor.html
Answer #2
commview?