说明：  基于DES和RSA的加密聊天工具，共包含4个文件: chat.cpp、des.h、rsa.h、makefile。 编译：命令行模式下，切换到代码所在目录，输入make后回车即可。 运行：命令行模式下输入 ./chat，然后选择程序执行角色（客户端或服务器），如选择服务器，则程序自动打开端口开始监听；如选择客户端，则需要输入服务器地址。最后输入命令quit退出程序。 此外，代码中实现了异步，select以及普通三种IO模型，需要通过定义宏控制。
(DES and RSA encryption based chat tool contains four files: chat.cpp, des.h, rsa.h, makefile. Compile: command line mode, switch to the code directory, enter make press Enter. Run: Command line mode input/chat, and then select the program to perform the role (client or server), such as selecting a server, the program automatically opens the port to start listening If you choose a client, you need to enter the server address. Finally, enter the quit command to exit the program. In addition, the code is implemented asynchronously, select and general three kinds of IO model, you need by defining the macro control.)