rresvport.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

/* posix */
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <time.h>

/* socket extensions */
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/un.h>

int
rresvport(int *p)
{
	int fd;
	short i;
	struct	sockaddr_in in;
	static int next;

	fd = socket(PF_INET, SOCK_STREAM, 0);
	if(fd < 0)
		return -1;
	i = 600 + ((getpid()+next++)%(1024-600));
	memset(&in, 0, sizeof(in));
	in.sin_family = AF_INET;
	in.sin_port = htons(i);
printf("in.sin_port = %d\n", in.sin_port);
	if(bind(fd, &in, sizeof(in)) < 0){
		close(fd);
		return -1;
	}
	if(p)
		*p = i;
	return fd;
}