C/C++ Socket UDP 广播消息的发送与接收

C/C++ Socket UDP 广播消息的发送与接收

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局域网内全网段广播消息的IP地址为：255.255.255.255，向该IP地址发送广播消息，局域网下的任何网段的客户机都能收到广播。

对于发送端，如果你只想给某个特定的网段发送消息，例如你的IP地址为192.168.31.107，那么你的广播地址是192.168.31.255，向该广播地址发送广播消息，只有192.168.31.XXX网段下的客户机能收到广播。

同样，对于接收端，绑定了广播地址0.0.0.0这个IP即可。

C语言 UDP 广播简单示例（linux系统下）：

/*
 * main.c
 *
 *  Created on: Sep 26, 2022
 *      Author: root
 */

#include 
#include 
#include 
#include 
#include 
#include 

#define BOARDCAST_IP     "255.255.255.255"
#define BOARDCAST_PORT   10130

int broadcast_send(void)
{
	int fd;
	int ret;
	int on;
	struct sockaddr_in addr;
	const char* message = "This is boardcast message !";

	fd = socket(AF_INET, SOCK_DGRAM, 0);

	if(fd < 0)
	{
		fprintf(stderr, " create socket failed ! \n");
		goto __exit;
	}

	on = 1;
	ret = setsockopt(fd, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on));
	if(ret < 0)
	{
		fprintf(stderr, " setsockopt failed ! \n");
		goto __exit;
	}

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

	addr.sin_family = AF_INET;
	addr.sin_port = htons(BOARDCAST_PORT);
	addr.sin_addr.s_addr = inet_addr(BOARDCAST_IP);

	ret = sendto(fd, message, strlen(message), 0, (struct sockaddr *)&addr, sizeof(addr));
	if(fd < 0)
	{
		fprintf(stderr, " boardcast failed ! \n");
		goto __exit;
	}

	printf(" send ok ! \n");

__exit:
	close(fd);
	return 0;
}

int broadcast_recv(void)
{
	int fd;
	int ret;
	int on;
	struct sockaddr_in addr, addr_from;
	char message[512];
	socklen_t len;

	fd = socket(AF_INET, SOCK_DGRAM, 0);

	if(fd < 0)
	{
		fprintf(stderr, " create socket failed ! \n");
		goto __exit;
	}

	on = 1;
	ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
	if(ret < 0)
	{
		fprintf(stderr, " setsockopt failed ! \n");
		goto __exit;
	}

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

	addr.sin_family = AF_INET;
	addr.sin_port = htons(BOARDCAST_PORT);
	addr.sin_addr.s_addr = htonl(INADDR_ANY);

	ret = bind(fd, (struct sockaddr *)&addr, sizeof(addr));
	if(ret < 0)
	{
		fprintf(stderr, " bind failed ! \n");
		goto __exit;
	}

	memset(message, 0X00, sizeof(message));

	len = sizeof(addr_from);
	ret = recvfrom(fd, message, sizeof(message), 0, (struct sockaddr *)&addr_from, &len);
	if(ret < 0)
	{
		fprintf(stderr, " recv failed ! \n");
		goto __exit;
	}

	printf(" recv: [%s] ok ! \n", message);

__exit:
	close(fd);
	return 0;
}

int main(int argc, const char* argv[])
{
	if(argc == 2)
	{
		if(strcmp(argv[1], "recv") == 0)
		{
			broadcast_recv();
		}

		if(strcmp(argv[1], "send") == 0)
		{
			broadcast_send();
		}
	}else
	{
		printf("\r\n");
		printf("########################################### \r\n");
		printf("Usage: %s [ recv | send ] \r\n", argv[0]);
		printf("e.g. : %s recv\r\n", argv[0]);
		printf("e.g. : %s send\r\n", argv[0]);
		printf("########################################### \r\n");
	}

	return 0;
}

程序运行结果：

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