嵌入式 Linux下进行广播包交互示例

服务器端也就是接受广播包：

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <fcntl.h>
#include <linux/in.h>
#include <stdlib.h>
/**
广播接收端代码
**/
#define IP_FOUND "IP_FOUND"
#define IP_FOUND_ACK "IP_FOUND_ACK"
#define PORT 9999

int main(int argc,char*argv[]){
int ret=-1;
int sock;
struct sockaddr_in server_addr;//服务器端地址
struct sockaddr_in from_addr;//客户端地址
int from_len=sizeof(struct sockaddr_in);
int count=-1;
fd_set readfd;//读文件描述符集合
char buffer[1024];
struct timeval timeout;
timeout.tv_sec=2;
timeout.tv_usec=0;
sock=socket(AF_INET,SOCK_DGRAM,0);//建立数据报套接字
if(sock<0){
perror("sock error");
return;
}

memset((void*)&server_addr,0,sizeof(struct sockaddr_in));
server_addr.sin_family=AF_INET;
server_addr.sin_addr.s_addr=htons(INADDR_ANY);
server_addr.sin_port=htons(PORT);
//将地址结构绑定到套接字上./
ret=bind(sock,(struct sockaddr*)&server_addr,sizeof(server_addr));
if(ret<0){
perror("bind error");
return;
}

while(1){
printf("=============================Recv Broadcast===================================\n");
timeout.tv_sec=2;
timeout.tv_usec=0;
//文件描述符集合清0
FD_ZERO(&readfd);
//将套接字描述符加入到文件描述符集合
FD_SET(sock,&readfd);
//select侦听是否有数据到来
ret=select(sock+1,&readfd,NULL,NULL,&timeout);//侦听是否可读
printf("ret=%d\n",ret);
switch(ret){
case -1://发生错误
break;
case 0://超时
printf("timeout\n");
break;
default:
if(FD_ISSET(sock,&readfd)){
count=recvfrom(sock,buffer,1024,0,(struct sockaddr*)&from_addr,&from_len);//接收客户端发送的数据
//from_addr保存客户端的地址结构
if(strstr(buffer,IP_FOUND)){
//响应客户端请求
//打印客户端的IP地址
printf("Client IP is %s\n",(char *)inet_ntoa(from_addr.sin_addr));
//打印客户端的端口号
printf("Client Send Port:%d\n",ntohs(from_addr.sin_port));
memcpy(buffer,IP_FOUND_ACK,strlen(IP_FOUND_ACK)+1);
count=sendto(sock,buffer,strlen(buffer),0,(struct sockaddr*)&from_addr,from_len);//将数据发送给客户端
}

}
break;
}
}
return;
}

客户端发送广播查找服务器：

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

/**
客户端实现广播

**/
#define IP_FOUND "IP_FOUND"
#define IP_FOUND_ACK "IP_FOUND_ACK"
#define IFNAME "eth0"
#define MCAST_PORT 9999
#define MAX_BROADCAST_NUM 16

int main(int argc,char*argv[]){
int ret=-1;

struct sockaddr_in from_addr;//服务端地址
int from_len=sizeof(from_addr);
int count=-1;
fd_set readfd;//读文件描述符集合
char buffer[1024];
struct timeval timeout;
timeout.tv_sec=2;//超时时间为2秒
timeout.tv_usec=0;

int sock=-1;
sock=socket(AF_INET,SOCK_DGRAM,0);//建立数据报套接字
if(sock<0){
printf("HandleIPFound:sock init error\n");
return;
}

//将使用的网络接口名字复制到ifr.ifr_name中，由于不同的网卡接口的广播地址是不一样的，因此指定网卡接口
struct ifreq ifr;

bzero(&ifr, sizeof(ifr));
//strcpy(ifr.ifr_name, "eth0");
strncpy(ifr.ifr_name,IFNAME,strlen(IFNAME));

//发送命令，获得网络接口的广播地址
if(ioctl(sock,SIOCGIFBRDADDR,&ifr)==-1){
perror("ioctl error");
return;
}

//将获得的广播地址复制到broadcast_addr
int so_broadcast=1;
struct sockaddr_in broadcast_addr;//广播地址
memcpy(&broadcast_addr,&ifr.ifr_broadaddr,sizeof(struct sockaddr_in));

//设置广播端口号
printf("broadcast IP is:%s\n",inet_ntoa(broadcast_addr.sin_addr));
broadcast_addr.sin_family=AF_INET;
broadcast_addr.sin_port=htons(MCAST_PORT);
//默认的套接字描述符sock是不支持广播，必须设置套接字描述符以支持广播
ret=setsockopt(sock,SOL_SOCKET,SO_BROADCAST,&so_broadcast,sizeof(so_broadcast));

while(1)
{
sleep(1);
printf("=====================================Send Broadcast========================================\n");
//发送多次广播，看网络上是否有服务器存在
int times = 1;
int i=0;
for(i=0;i<times;i++){//一共发送10次广播，每次等待2秒是否有回应
//广播发送服务器地址请求
timeout.tv_sec=2;//超时时间为2秒
timeout.tv_usec=0;
ret=sendto(sock,IP_FOUND,strlen(IP_FOUND),0,(struct sockaddr*)&broadcast_addr,sizeof(broadcast_addr));
if(ret==-1){
continue;
}

//文件描述符清0
FD_ZERO(&readfd);
//将套接字文件描述符加入到文件描述符集合中
FD_SET(sock,&readfd);
//select侦听是否有数据到来
ret=select(sock+1,&readfd,NULL,NULL,&timeout);
switch(ret){
case -1:
break;
case 0:
printf("timeout\n");
break;
default:
//接收到数据
if(FD_ISSET(sock,&readfd)){
memset(buffer,0,1024);
count=recvfrom(sock,buffer,1024,0,(struct sockaddr*)&from_addr,&from_len);//from_addr为服务器端地址
strcpy((buffer+strlen(buffer)),"\0");

printf("recvmsg is %s ,The length of recvmsg is %d\n",buffer,strlen(buffer));
if(strstr(buffer,IP_FOUND_ACK)){
printf("found server IP is:%s\n",inet_ntoa(from_addr.sin_addr));
//服务器端的发送端口号
printf("Server Port:%d\n",htons(from_addr.sin_port));
}
}
break;

}
}

}
return;
}

注意：

1、程序是死循环完成接收或者发送广播包

2、程序没有内存泄漏问题

3、程序没有接收乱码的问题服务器端运行效果:

=====================================Send Broadcast========================================

recvmsg is IP_FOUND_ACK ,The length of recvmsg is 12

found server IP is:10.10.2.59

Server Port:9999

=====================================Send Broadcast========================================

recvmsg is IP_FOUND_ACK ,The length of recvmsg is 12

found server IP is:10.10.2.59

Server Port:9999

客户端运行效果：

=============================Recv Broadcast===================================

ret=1

Client IP is 10.10.2.59

Client Send Port:33784

=============================Recv Broadcast===================================

ret=1

Client IP is 10.10.2.155

Client Send Port:38542