How do we use our website as a chat room with the 4 of us posting and all 4 see what the others post like IMs

We are trying to use our website like a chat room, where we can all be at our website at the same time and post messages and all of us be able to see what the others are writing at the same time, very similar to an IM where it is a running conversation, but an IM is between two people. We have 4 and if all else fails we know we can simply post messages back and forth at the website.