java写的文件服务软件，当一个客户端连接到服务器，服务器从客户端读取一条命令。判断客户端请求是一个文件还是‘index’，如果是‘index’就发送文件列表。如果是请求一个确定文件，判断文件是否存在，如果存在就发送‘ok’，并发送该文件给客户端，如果不存在就发生‘error’。-java file services to write the software, when a client connects to the server, the server reads a command from the client. Determine the client requests a file or　index , if it is　index　to send the file list. To determine if a file is requested to determine whether a file exists and if it sends the　ok , and send the file to the client, if the place does not exist　error .