基于TCP and UDP的socket编程

简单的Client/Server网络应用程序。要求实现客户向服务器传输任意一个字符串，服务器将收到的字符串变换成大写后传回客户。

2.修改上述程序，实现服务器根据客户请求，将服务器端指定的文件可靠地传输给客户。如果服务器没有指定的文件，服务器将给客户返回一个信息，通知客户其请求文件不存在。

-TCP and UDP socket programming

Simple Client/Server network applications. Required to achieve customer transmitted to the server, any string, the server will receive the string returned customers transform to uppercase.

(2) modify the above procedure, the server according to customer requests, the reliable transmission of the file to the specified server to the customer. If the server does not have the specified file, the server will return a message to inform customers of its requested file does not exist.