聊天程序主要利用Java网络包中的服务器套接字和客户端套接字实现，其核心部分的实现思路如下：

服务器根据指定的端口创建服务器套接字，并在该端口侦听连接请求；

每一个新加入的客户端创建客户端套接字，与服务器进行连接；

每一个连接在服务器有一个连接池保持连接；

当其中的一个客户端发出群聊或者上线下线信息后，对应的连接的服务器程序在接收到该消息后，向其所维持的所有的客户连接广播该消息。当客户端发出单独聊天，文件传输等需要发给指定用户的消息时，服务器端遍历连接池找到对应客户端，将消息单独发给该客户端。-Chat program using mainly Java network package server socket and client socket implementation, the core part of the implementation ideas are as follows: the server according to the specified port to create a server socket and listens for connection requests on this port　each a new client create a client socket connection with the server　each one connected to the server has a connection pool to stay connected　When one client sends a group chat or offline on-line information, the corresponding connection server program receives the message, to maintain all of its client connection broadcasts the message. When the client makes a separate chat, file transfer and other users need to specify a message sent to the server-side connection pooling find the corresponding traversal client, the message is sent separately to the client.