What could be done to these computers?

Hello,
What happens when a computer that is locally connected can send packet data but cannot receive?

i have four computers that are locally connected. two of them can send packet data but cannot receive while the other two are working perfectly. the two faulty computers can connect to the local network but when they try to view other devices or computers on the network they see none, also other devices and the other computers cannot also see it on the network. these computers are used to share files and folders. what could be wrong?