*使用select函数可以以非阻塞的方式和多个socket通信。程序只是演示select函数的使用，即使某个连接关闭以后也不会修改当前连接数，连接数达到最大值后会终止程序。

1. 程序使用了一个数组fd，通信开始后把需要通信的多个socket描述符都放入此数组

2. 首先生成一个叫sock_fd的socket描述符，用于监听端口。

3. 将sock_fd和数组fd中不为0的描述符放入select将检查的集合fdsr。

4. 处理fdsr中可以接收数据的连接。如果是sock_fd，表明有新连接加入，将新加入连接的socket描述符放置到fd。 */

// select_server.c-* use Select function with non blocking mode and multiple socket communication. The program is the use of demonstration of select function, even if a connection is closed will not modify the current number of connections, the number of connections after reaching the maximum value will terminate the program.

1 procedures for the use of an array of FD, communication after the start of the multiple socket descr iptor communication in this array

2 first generate a call sock_fd socket descr iptor, for listening port.

3 the sock_fd and array FD is not 0 descr iptors in select will check the set fdsr.

4 fdsr can be connected to receive data. If sock_fd, indicates that there is a new connection to join, will join the new connection socket descr iptor is placed into the fd.*

//select_server.c