网络编程-socket接收udp组播报文

socket接收组播报文主要有两个操作：

1、将组播地址bind到socket句柄上

2、根据IGMP协议通过IP_ADD_MEMBERSHIP向外发出JION帧

具体实例代码如下：

udp_group_server.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <unistd.h>

int main(int argc, char *argv[])
{
	int ret;
	char recv_buf[1024];
	int length=0;
	struct sockaddr_in sender;
	int sender_len = sizeof(sender);
	char group[16]="224.0.0.88";
	struct sockaddr_in local_addr;
	struct ip_mreq mreq;

	int sock = socket(AF_INET,SOCK_DGRAM,0);
	if(sock<0)
	{
		printf("socket failed.\n");
		return 2;
	}

	memset(&local_addr,0,sizeof(local_addr));

	local_addr.sin_family = AF_INET;
	local_addr.sin_addr.s_addr = htonl(INADDR_ANY);
	local_addr.sin_port = htons(8888);

	ret = bind(sock,(struct sockaddr *)&local_addr,sizeof(local_addr));
	if(ret<0)
	{
		perror("bind failed.\n");
		return 3;
	}

	mreq.imr_multiaddr.s_addr = inet_addr(group);
	mreq.imr_interface.s_addr = htonl(INADDR_ANY);

	/*
	 * IP_ADD_MEMBERSHIP will send jion frame to the network device for joining the group network.
	 * Then the network device will send multi-frames to the client.
	 */

	ret=setsockopt(sock,IPPROTO_IP,IP_ADD_MEMBERSHIP,&mreq,sizeof(mreq));
	if(ret<0)
	{
		printf("setsockopt failed.\n");
		return 4;
	}else{
		printf("setsockopt success\n");
	}

	while(1)
	{
		memset(recv_buf,0,sizeof(recv_buf));
		length = recvfrom(sock,recv_buf,sizeof(recv_buf),0,(struct sockaddr *)&sender,&sender_len);
		recv_buf[length]='\0';
		printf("receive buffer: %s\n", recv_buf);
	}

	close(sock);
	return 0;
}

udp_group_client.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <unistd.h>

int main(int argc, char *argv[])
{
	char group_addr[16]="224.0.0.88";
	char buf[1024] = "This is a group udp.";
	int length=strlen(buf);
	struct sockaddr_in remote_addr;
	int sock = socket(AF_INET, SOCK_DGRAM, 0);
	if(sock<0)
	{
		printf("socket failed.\n");
		return 2;
	}

	memset(&remote_addr, 0, sizeof(remote_addr));

	remote_addr.sin_family = AF_INET;
	remote_addr.sin_addr.s_addr = inet_addr(group_addr);
	remote_addr.sin_port = htons(8888);

	length = sendto(sock,buf,strlen(buf),0,(struct sockaddr *)&remote_addr,sizeof(remote_addr));;
	printf("send %s\n", buf);
	
	close(sock);
	return 0;
}

Makefile:

all:udp_group_server udp_group_client

udp_group_server:
	gcc udp_group_server.c -o udp_group_server

udp_group_client:
	gcc udp_group_client.c -o udp_group_client

clean:
	rm -rf udp_group_client udp_group_server

编译并运行：

# make
gcc udp_group_server.c -o udp_group_server
gcc udp_group_client.c -o udp_group_client
# ./udp_group_server &
[1] 97800
# setsockopt success

# ./udp_group_client 
send This is a group udp.

receive buffer: This is a group udp.