目录
1 广播
1.1 什么是广播?
1.2 广播地址
1.3 广播的实现
2 组播
2.1 分类的IP地址
2.2 多播 IP 地址
2.3 组播的实现
1 广播
1.1 什么是广播?
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
1.2 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
 
1.3 广播的实现
广播的实现

sender.c
#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h> /* superset of previous */
#include <unistd.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <strings.h>
#include <string.h>
#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<multiaddr><port>", 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;
}
 
receiver.c
#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h> /* superset of previous */
#include <unistd.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <strings.h>
#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<addr><port>", 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;
}
 
2 组播
2.1 分类的IP地址

2.2 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。
 
2.3 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
 
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);
}
 
sender.c
#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h> /* superset of previous */
#include <unistd.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <strings.h>
#include <string.h>
#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<multiaddr><port>", 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;
}
 
receiver.c
#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h> /* superset of previous */
#include <unistd.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <strings.h>
#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<addr><port>", 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;
}
 
                


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