The last chapter discussed sockets from the standpoint of clients: programs that open a socket to a server that’s listening for connections. However, client sockets themselves aren’t enough; clients aren’t much use unless they can talk to a server, and the Socket class discussed in the last chapter is not sufficient for writing servers. To create a Socket, you need to know the Internet host to which you want to connect. When you’re writing a server, you don’t know in advance who will contact you, and even if you did, you wouldn’t know when that host wanted to contact you. In other words, servers are like receptionists who sit by the phone and wait for incoming calls. They don’t know who will call or when, only that when the phone rings, they have to pick it up and talk to whoever is there. You can’t program that behavior with the