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使用SIGURG信号接受带外数据

news 来源：原创 2024/5/8 6:44:01

这是一个服务器程序，使用SIGURG信号接受带外数据。

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

#define BUF_SIZE 1024

static int connfd;

/* SIGURG 信号的处理函数 */
void sig_urg(int sig)
{
	int save_errno = errno;
	char buffer[BUF_SIZE];
	memset(buffer, '\0', BUF_SIZE);
	int ret = recv(connfd, buffer, BUF_SIZE - 1, MSG_OOB);	/* 接收带外数据 */
	printf("got %d bytes of oob data '%s'\n", ret, buffer);
	errno = save_errno;
}

void addsig(int sig, void (*sig_handler)(int))
{
	struct sigaction sa;
	memset(&sa, '\0', sizeof(sa));
	sa.sa_handler = sig_handler;
	sa.sa_flags |= SA_RESTART;
	sigfillset(&sa.sa_mask);
	assert(sigaction(sig, &sa, NULL) != -1);
}

int main(int argc, char* argv[])
{
	if (argc <= 2)
	{
		return 1;
	}
	const char* ip = argv[1];
	int port = atoi(argv[2]);

	struct sockaddr_in address;
	bzero(&address, sizeof(address));
	address.sin_family = AF_INET;
	address.sin_port = htons(port);
	inet_pton(AF_INET, ip, &address.sin_addr);

	int sockfd = socket(PF_INET, SOCK_STREAM, 0);
	assert(sockfd >= 0);

	int ret = bind(sockfd, (struct sockaddr*)&address, sizeof(address));
	assert(ret != -1);

	ret = listen(sockfd, 5);
	assert(ret != -1);

	struct sockaddr_in client;
	socklen_t client_addrlen = sizeof(client);
	connfd = accept(sockfd, (struct sockaddr*)&client, &client_addrlen);
	if (connfd < 0)
	{
		printf("errno is: %d\n", errno);
	}
	else
	{
		addsig(SIGURG, sig_urg);
		/* 使用 SIGURG 信号之前，必须设置 socket 的宿主进程或进程组为当前进程，意思是：当该 socket 上有带外数据时，将 SIGURG 发送给那个进程或进程组 */
		fcntl(connfd, F_SETOWN, getpid());

		char buffer[BUF_SIZE];
		while (1)	/* 循环接受普通数据 */
		{
			memset(buffer, '\0', BUF_SIZE);
			ret = recv(connfd, buffer, BUF_SIZE - 1, 0);
			if (ret <= 0)
			{
				break;
			}
			printf("got %d bytes of normal data '%s'\n", ret, buffer);
		}
		close(connfd);
	}

	close(sockfd);
	return 0;
}