说明：  一个简单的http下载程序,用C++在linux下写了一个简单的http下载程序，程序的功能很简单，在终端输入文件所在网址，程序会单线程从服务器上下载该文件到本地。程序里面涉及了socket编程、http协议、二进制文件的写入。
(a simple http download and use under linux C wrote in a simple http download procedure is very simple function of the input terminal is located site will be single-threaded process from the server to download the file to the local. Inside the socket programming involved, http agreement, write a binary file.)