SMP End of Stream Severe Lag

While typically running the server, the computer's CPU is jacked way high, and the server repeatedly spams the message "[SEVERE] End of stream" with no apparent cause. The server lags, destroyed blocks reappear, and it consistently kicks players off stating "Internal Exception: java.net.SocketTimeoutException:Read timed out"

I have restarted the server multiple times, restarted the computer just as much, and the issue remains. I never have more than four people connected simultaneously, but the problems continue even when alone in the server. The kicks and lag specifically, however it seems smoother when it's one player at a time.