l8-d19 广播与组播

一、广播

1.概念

数据包发送方式只有一个接受方，称为单播

如果同时发给局域网中的所有主机，称为广播

只有用户数据报(使用UDP协议)套接字才能广播

广播地址

一个网络内主机号全为1的IP地址为广播地址

发到该地址的数据包被所有的主机接收

255.255.255.255在所有网段中都代表广播地址

int on = 1;

setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on));

2.实现

 发送端

#include 
#include 
#include 
#include  /* superset of previous */
#include 
#include 
#include 
#include 
#include 
 
#define ErrExit(msg) do {perror(msg); exit(EXIT_FAILURE);} while(0)
typedef struct sockaddr Addr;
typedef struct sockaddr_in Addr_in;
 
int main(int argc, char *argv[])
{
	int fd = -1;
	Addr_in peeraddr;
	socklen_t peerlen = sizeof(peeraddr);
	char buf[BUFSIZ] = {};
	/*参数检查*/
	if(argc < 3){
		fprintf(stderr, "%s", argv[0]);
		exit(EXIT_FAILURE);
	}
	/*创建套接字*/
	if( (fd = socket(AF_INET, SOCK_DGRAM, 0) ) < 0)
		ErrExit("socket");
 
	/*允许广播*/
	int on = 1;
	setsockopt(fd, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on));
 
	/*设置通信结构体*/
	peeraddr.sin_family = AF_INET;
	peeraddr.sin_port = htons(atoi(argv[2]));
	if(!inet_aton(argv[1], &peeraddr.sin_addr) ){
		fprintf(stderr, "Invalid address\n");
		exit(EXIT_FAILURE);
	}
	while(1){
		fgets(buf, BUFSIZ, stdin);
		sendto(fd, buf, strlen(buf)+1, 0, (Addr *)&peeraddr, peerlen);
	}
	return 0;
}
 

接收端

#include 
#include 
#include 
#include  /* superset of previous */
#include 
#include 
#include 
#include 
 
#define ErrExit(msg) do {perror(msg); exit(EXIT_FAILURE);} while(0)
typedef struct sockaddr Addr;
typedef struct sockaddr_in Addr_in;
 
int main(int argc, char *argv[])
{
	int fd = -1;
	Addr_in myaddr, peeraddr;
	socklen_t peerlen = sizeof(peeraddr);
	char buf[BUFSIZ] = {};
	/*参数检查*/
	if(argc < 3){
		fprintf(stderr, "%s", argv[0]);
		exit(EXIT_FAILURE);
	}
	/*创建套接字*/
	if( (fd = socket(AF_INET, SOCK_DGRAM, 0) ) < 0)
			ErrExit("socket");
	/*设置通信结构体*/
	myaddr.sin_family = AF_INET;
	myaddr.sin_port = htons(atoi(argv[2]));
	if(!inet_aton(argv[1], &myaddr.sin_addr) ){
		fprintf(stderr, "Invalid address\n");
		exit(EXIT_FAILURE);
	}
	/*绑定通信结构体*/
	if( bind(fd, (Addr *)&myaddr, sizeof(Addr_in)) )
		ErrExit("bind");
	while(1){
		recvfrom(fd, buf, BUFSIZ, 0, (Addr *)&peeraddr, &peerlen);
		printf("[%s:%d]%s\n", inet_ntoa(peeraddr.sin_addr), ntohs(peeraddr.sin_port), buf);
	}
	return 0;
}
 

二、组播

1.概念

多播 IP 地址

        在 IP 多播数据报的目的地址需要写入多播组的标识符。

        多播组的标识符就是 IP 地址中的 D 类地址（多播地址）。

        地址范围：224.0.0.0 ~ 239.255.255.255

        每一个 D 类地址标志一个多播组。

        多播地址只能用于目的地址，不能用于源地址。

组播的实现

        创建用户数据报套接字

        加入多播组

        绑定组播IP地址和端口

        等待接收数据

多个网卡

struct ip_mreqn {

    struct in_addr imr_multiaddr;  /*IP 组播组地址*/

    struct in_addr imr_address;   /*本地接口的IP地址*/

    int                   imr_ifindex;   /*本地网卡的编号*/

}

if(setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0){

perror("setsockopt");

exit(0);

}

单一网卡

struct ip_mreq {

    struct in_addr imr_multiaddr;  /*IP 组播组地址*/

    struct in_addr imr_address;   /*本地接口的IP地址*/

}

if(setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0){

perror("setsockopt");

exit(0);

}

2.实现

接收端

#include 
#include 
#include 
#include  /* superset of previous */
#include 
#include 
#include 
#include 
 
#define ErrExit(msg) do {perror(msg); exit(EXIT_FAILURE);} while(0)
typedef struct sockaddr Addr;
typedef struct sockaddr_in Addr_in;
 
int main(int argc, char *argv[])
{
	int fd = -1;
	Addr_in myaddr, peeraddr;
	socklen_t peerlen = sizeof(peeraddr);
	struct ip_mreqn mreq;
	char buf[BUFSIZ] = {};
	/*参数检查*/
	if(argc < 3){
		fprintf(stderr, "%s", argv[0]);
		exit(EXIT_FAILURE);
	}
	/*创建套接字*/
	if( (fd = socket(AF_INET, SOCK_DGRAM, 0) ) < 0)
			ErrExit("socket");
	/*加入多播组*/
	bzero(&mreq, sizeof(mreq) );
	if(!inet_aton(argv[1], &mreq.imr_multiaddr) ){
		fprintf(stderr, "Invalid address\n");
		exit(EXIT_FAILURE);
	}
	if(setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0){
		perror("setsockopt");
		exit(0);
	}
 
	/*设置通信结构体*/
	myaddr.sin_family = AF_INET;
	myaddr.sin_port = htons(atoi(argv[2]));
	if(!inet_aton(argv[1], &myaddr.sin_addr) ){
		fprintf(stderr, "Invalid address\n");
		exit(EXIT_FAILURE);
	}
	/*绑定通信结构体*/
	if( bind(fd, (Addr *)&myaddr, sizeof(Addr_in)) )
		ErrExit("bind");
	while(1){
		recvfrom(fd, buf, BUFSIZ, 0, (Addr *)&peeraddr, &peerlen);
		printf("[%s:%d]%s\n", inet_ntoa(peeraddr.sin_addr), ntohs(peeraddr.sin_port), buf);
	}
	return 0;
}
 

发送端

#include 
#include 
#include 
#include  /* superset of previous */
#include 
#include 
#include 
#include 
#include 
 
#define ErrExit(msg) do {perror(msg); exit(EXIT_FAILURE);} while(0)
typedef struct sockaddr Addr;
typedef struct sockaddr_in Addr_in;
 
int main(int argc, char *argv[])
{
	int fd = -1;
	Addr_in peeraddr;
	socklen_t peerlen = sizeof(peeraddr);
	char buf[BUFSIZ] = {};
	/*参数检查*/
	if(argc < 3){
		fprintf(stderr, "%s", argv[0]);
		exit(EXIT_FAILURE);
	}
	/*创建套接字*/
	if( (fd = socket(AF_INET, SOCK_DGRAM, 0) ) < 0)
		ErrExit("socket");
 
	/*设置通信结构体*/
	peeraddr.sin_family = AF_INET;
	peeraddr.sin_port = htons(atoi(argv[2]));
	if(!inet_aton(argv[1], &peeraddr.sin_addr) ){
		fprintf(stderr, "Invalid address\n");
		exit(EXIT_FAILURE);
	}
	while(1){
		fgets(buf, BUFSIZ, stdin);
		sendto(fd, buf, strlen(buf)+1, 0, (Addr *)&peeraddr, peerlen);
	}
	return 0;
}
 

Makefile

CC=gcc
CFLAGS=-g -Wall
all:receiver sender

clean:
    -rm receiver sender