10-5broadcast_r.c

#include <stdio.h> 
#include <arpa/inet.h> 
#include <sys/types.h>
#include <sys/socket.h> 
#include <netinet/in.h>
#include <stdlib.h> 
#include <unistd.h> 
#include <string.h>

#define N 128
#define errlog(errmsg) do{perror(errmsg);\
						  printf("%s--%s--%d\n",\
								  __FILE__, __func__, __LINE__);\
						  exit(1);\
					     }while(0)

int main(int argc, const char *argv[])
{
	int sockfd;
	struct sockaddr_in broadcastaddr, addr;
	socklen_t addrlen = sizeof(broadcastaddr);
	char buf[N] = {};

	if(argc < 3)
	{
		fprintf(stderr, "Usage: %s ip port\n", argv[0]);
		exit(1);
	}

	//第一步:创建套接字
	if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
	{
		errlog("fail to socket");
	}

	//第二步:填充广播网络信息结构体
	//inet_addr:将点分十进制ip地址转化为网络字节序的整形数据
	//htons:将主机字节序转化为网络字节序
	//atoi:将数字形字符串转化为整形数据
	broadcastaddr.sin_family = AF_INET;
	broadcastaddr.sin_addr.s_addr = inet_addr(argv[1]);
	broadcastaddr.sin_port = htons(atoi(argv[2]));

	//第三步:将套接字与服务器网络信息结构体绑定
	if(bind(sockfd, (struct sockaddr *)&broadcastaddr, addrlen) < 0)
	{
		errlog("fail to bind");
	}

	ssize_t bytes;
	while(1)
	{
		if((bytes = recvfrom(sockfd, buf, N, 0,\ 
						(struct sockaddr *)&addr, &addrlen)) < 0)
		{
			errlog("fail to recvfrom");
		}
		else 
		{
			printf("ip: %s, port: %d\n",\ 
					inet_ntoa(addr.sin_addr),\ 
					ntohs(addr.sin_port));

			printf("broadcast : %s\n", buf);

		}
	}

	close(sockfd);
	
	return 0;
}