Nobody can connect to my bukkit server

No one except me can connect to my server. I am using the same computer as the server is running from and I can connect. The problem is that no one else can. Four people have tried and none of them can. They connect but before they join they time out. I am using my Ipv4 IP. I don't know if my ports are forwarded or not.

Thanks for your help,
NickHaldon