linux下怎么使用C语言编写接收和发送udp组播数据？

一，发送端

代码如下：

先调用initUdpMultiCastSender初始化，

int initUdpMultiCastSender(uint32_t localip,uint16_t localport)
{
	int sockfd = socket(AF_INET,SOCK_DGRAM,0);
	if (-1 == sockfd)
	{
		printf("[initUdpMultiCastSender]socket fail\n");
		return -1;
	}

	struct sockaddr_in myaddr;
	memset(&myaddr,0,sizeof(myaddr));
	myaddr.sin_family = AF_INET;
	myaddr.sin_port = htons(localport);
	myaddr.sin_addr.s_addr = localip;
	int bindret = bind(sockfd,(struct sockaddr *)(&myaddr),sizeof(struct sockaddr));
	if (-1 == bindret)
	{
		perror("[initUdpMultiCastSender]bind fail\n");
		close(sockfd);
		return -1;
	}
	return sockfd;
}

后使用sendUdpMultiCast发送数据，

int sendUdpMultiCast(int sockfd,char *pMultiCastIp,uint16_t multicastPort,void *data,uint32_t len)
{
	struct sockaddr_in destAddr;
	destAddr.sin_family = AF_INET;
	destAddr.sin_addr.s_addr = inet_addr(pMultiCastIp);
	destAddr.sin_port = htons(multicastPort);
	int sendLen = sendto(sockfd,data,len,0,(struct sockaddr *)(&destAddr),sizeof(struct sockaddr));
	return sendLen;
}

发送端的代码，整体的思路就是创建socket->绑定本地ip,port（注意，该port不是组播port，而是本地port，指定个未使用的即可）->发送数据（注意，发送的ip和port为组播ip,port）

二、接收端

	int sockfd = socket(AF_INET,SOCK_DGRAM,0);
	if (-1 == sockfd)
	{
		perror("socket fail\n");
		return -3;
	}
	printf("socket succ\n");

	struct ip_mreq mreq;
	memset(&mreq,0,sizeof(struct ip_mreq));
	mreq.imr_interface.s_addr = htonl(INADDR_ANY);
	mreq.imr_multiaddr.s_addr = inet_addr(pUdpMultiCastIp);

	int setoptret = setsockopt(sockfd,IPPROTO_IP,IP_ADD_MEMBERSHIP,&mreq,sizeof(struct ip_mreq));
	if (-1 == setoptret)
	{
		perror("setsockopt fail\n");
		return -4;
	}
	printf("setsockopt ip_add_membership succ\n");

	struct sockaddr_in peeraddr;
	memset(&peeraddr,0,sizeof(struct sockaddr_in));
	peeraddr.sin_family = AF_INET;
	peeraddr.sin_addr.s_addr = inet_addr(pUdpMultiCastIp);
	peeraddr.sin_port = htons(udpMultiCastPort);

	int bindRet = bind(sockfd,(struct sockaddr *)(&peeraddr),sizeof(struct sockaddr));
	if (-1 == bindRet)
	{
		perror("bind fail\n");
		return -5;
	}
	printf("bind succ\n");

	while(1)
	{
		char buffer[1024] = {0};
		socklen_t addrLen = sizeof(struct sockaddr);
		printf("ready 2 recv\n");
		int recvRet = recvfrom(sockfd,buffer,sizeof(buffer)-1,0,(struct sockaddr*)(&peeraddr),&addrLen);
		if (-1 == recvRet)
		{
			perror("recvfrom fail\n");
			break;
		}
		printf("recvfrom succ,buffer is %s\n",buffer);
	}

接收端的代码，整体的思路就是创建socket->加入组播（本地地址和组播地址赋值给mreq）->绑定ip,port（注意，该ip和port是组播ip和组播port）->接收数据（注意，接收的ip和port为组播ip,port）