SIGURG信号 -- 带外数据的处理

使用SIGURG处理带外数据程序实例：

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

#define BUFSIZE 1024

static int connfd;

/*SIGURG信号处理函数*/
void sig_urg(int urg)
{
int save_errno = errno;
char buffer[BUFSIZE];
    memset(buffer, '\0', BUFSIZE);
int ret = recv(connfd, buffer, BUFSIZE-1 , MSG_OOB);/*MSG_OOB标志 接收带外数据*/
    printf("接收到%d数据:%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)
    {
        printf("Args err");
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;
    inet_pton(AF_INET, ip, &address.sin_addr);
    address.sin_port = htons(port);

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

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

struct sockaddr_in client;
    socklen_t client_addrlength = sizeof(client);
    connfd = accept(sock, (struct sockaddr*)&client, &client_addrlength);
    if(connfd < 0)
    {
        printf("errno is %d\n", errno);
    }
else
    {
/*捕捉到SIGURG则执行sig_urg信号处理函数*/
        addsig(SIGURG, sig_urg);
/*使用SIGURG信号前，必须设置socket的宿主进程或进程组，设为当前进程*/
        fcntl(connfd, F_SETOWN, getpid());

char buffer[BUFSIZE];
/*普通数据入口*/
while(1)
        {
            memset(buffer, '\0', BUFSIZE);

            ret = recv(connfd, buffer, BUFSIZE-1,0);
            if(ret <= 0)
            {
break;
            }
            printf("接收到%d数据:%s\n", ret, buffer);
        }
        close(connfd);
    }
    close(sock);

return 0;
}

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