lv8 嵌入式开发-网络编程开发 18 广播与组播的实现
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;
}