组播这个东西,很多年前用过一次。本身的原理不复杂,未知的是使用的环境,受使用环境的影响有多大,还是那句废话,具体问题具体分析。
发送端代码multicast.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#define MULTICAST_ADDR "224.0.0.1" // 组播地址
#define MULTICAST_PORT 9990 // 组播端口
int main(int argc, char *argv[]) {
int sockfd;
struct sockaddr_in local,addr;
char message[] = "Hello, multicast!";
// 1. 创建UDP套接字
if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
perror("socket creation failed");
exit(EXIT_FAILURE);
}
// 2. 设置套接字选项以允许组播
int reuse = 1;
if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(reuse)) < 0) {
perror("setsockopt (SO_REUSEADDR) failed");
exit(EXIT_FAILURE);
}
int yes = 1;
if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1) {
perror("setsockopt");
exit(1);
}
// 3. 绑定套接字(可选,通常不需要)
// ...
local.sin_family = AF_INET;
// 假设你想绑定到本地的IP地址 "192.168.1.100",你可以通过inet_addr或inet_pton来设置
local.sin_addr.s_addr = inet_addr("192.168.0.3");
// 或者使用inet_pton来处理IPv6地址
// if (inet_pton(AF_INET, "192.168.0.3", &serv_addr.sin_addr) <= 0) {
// perror("inet_pton failed");
// exit(EXIT_FAILURE);
// }
local.sin_port = htons(12345); // 假设端口是12345
// 4. 构造组播地址结构
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = inet_addr(MULTICAST_ADDR);
addr.sin_port = htons(MULTICAST_PORT);
// 5. 发送数据
if (sendto(sockfd, message, strlen(message), 0, (const struct sockaddr *)&addr, sizeof(addr)) < 0) {
perror("sendto failed");
exit(EXIT_FAILURE);
}
// 6. 接收数据(如果需要)
// ...
// 7. 关闭套接字
close(sockfd);
return 0;
}
接收端代码multicast_recv.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#define MULTICAST_ADDR "224.0.0.1" // 组播地址
#define MULTICAST_PORT 9990 // 组播端口
#define BUFFER_SIZE 1024 // 接收缓冲区大小
int main(int argc, char *argv[]) {
int sockfd;
struct sockaddr_in addr;
char buffer[BUFFER_SIZE];
struct ip_mreq mreq;
socklen_t addrlen = sizeof(addr);
// 1. 创建UDP套接字
if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
perror("socket creation failed");
exit(EXIT_FAILURE);
}
int yes = 1;
if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1) {
perror("setsockopt");
exit(1);
}
// 2. 设置组播地址和端口
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(INADDR_ANY); // 绑定到所有可用的网络接口
addr.sin_port = htons(MULTICAST_PORT);
// 3. 绑定套接字(如果需要特定的端口,就绑定;否则,通常不需要绑定)
if (bind(sockfd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
perror("bind failed");
exit(EXIT_FAILURE);
}
// 4. 设置组播选项
mreq.imr_multiaddr.s_addr = inet_addr(MULTICAST_ADDR);
mreq.imr_interface.s_addr = htonl(INADDR_ANY); // 或者设置为特定的网络接口IP
if (setsockopt(sockfd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0) {
perror("setsockopt failed");
exit(EXIT_FAILURE);
}
// 5. 接收数据
printf("Waiting for multicast packets...\n");
while (1) {
int nbytes = recvfrom(sockfd, buffer, BUFFER_SIZE, 0, (struct sockaddr *)&addr, &addrlen);
if (nbytes < 0) {
perror("recvfrom failed");
exit(EXIT_FAILURE);
}
buffer[nbytes] = '\0'; // 确保字符串以null字符结尾
printf("Received: %s\n", buffer);
}
// 6. 关闭套接字(注意:由于我们在一个无限循环中,这行代码实际上不会被执行)
close(sockfd);
return 0;
}
编译脚本:
#!/bin/bash
echo "hello"
source /opt/fsl-imx-xwayland/5.4-zeus/environment-setup-aarch64-poky-linux
echo $ARCH
aarch64-poky-linux-gcc --sysroot=/opt/fsl-imx-xwayland/5.4-zeus/sysroots/aarch64-poky-linux multicast.c -o multicast
gcc multicast_recv.c -o multicast_recv
sudo cp multicast /home/lkmao/nfsroot/yocto/home/root/
#make
exit 0
设置网关:
测试发现,如果不设置网关,组播数据发不出去。
route add default gw 192.168.0.1 dev eth1
root@imx8mpevk:~# route add default gw 192.168.0.1 dev eth1
root@imx8mpevk:~# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.0.1 0.0.0.0 UG 0 0 0 eth1
0.0.0.0 0.0.0.0 0.0.0.0 U 0 0 0 eth0
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
root@imx8mpevk:~#
测试结果
使用nc作为接收端测试
测试的时候,发现,直接监听udp的9990端口就可以,这个有点诧异啊。
nc -ul 9990
组播地址查看
ip maddr show
开发板的地址:
root@imx8mpevk:~# ip maddr show dev eth1
3: eth1
link 33:33:00:00:00:01
link 01:00:5e:00:00:01
link 33:33:ff:07:0b:a5
link 33:33:00:00:02:02
link 33:33:00:00:00:fb
link 01:00:5e:00:00:fb
inet 224.0.0.251
inet 224.0.0.1
inet6 ff02::fb
inet6 ff02::202
inet6 ff02::1:ff07:ba5
inet6 ff02::1
inet6 ff01::1
root@imx8mpevk:~#
ubuntu的广播查询:
lkmao@lkmao-virtual-machine:~$ ip maddr show dev ens33
2: ens33
link 01:00:5e:00:00:01
link 33:33:00:00:00:01
link 33:33:ff:9a:b7:5a
link 01:00:5e:00:00:fb
link 33:33:00:00:00:fb
inet 224.0.0.251
inet 224.0.0.1
inet6 ff02::fb
inet6 ff02::1:ff9a:b75a
inet6 ff02::1
inet6 ff01::1
lkmao@lkmao-virtual-machine:~$
根据执行命令可知,默认的组播组都是224.0.0.1,这也说明了,为什么直接执行nc -ul 9990可以接收到组播数据。
小结
这个还得具体问题具体分析吧。