What is this in my logs (dupes,error-overflow)

[morkel]

Can anyone what is this (duplicate connection) and (Overflow)??

[SELECT ALL] Code:

[x.x.x.x] client connected
[x.x.x.x] robisswat logged in (default), AC: 1104|840[x.x.x.x] disconnecting client robisswat (duplicate connection) cn 0, 202seconds played, score saved
[x.x.x.x] client connected
[x.x.x.x] tavinho logged in (default), AC: 1104|840[x.x.x.x] disconnecting client tavinho (duplicate connection) cn 1, 203 seconds played, score saved
[x.x.x.x] client connected
[x.x.x.x] disconnected client player29(error-overflow) cn 3, 75 seconds played, score saved

Many clients are disconnected for same reason's from my server
MOd edit:all ips are not shown.