linux进程线程间通信：传递文件描述符 - 知否问答 - 万象云+社区

struct mypara { int tcp_sock;//参数1 int pip_sock;//参数2 }; int main(int argc, char const *argv[]) { int serv_sock; struct sockaddr_in serv_adr; pthread_t t_id[NUM_THREAD]; int j,k,state,str_len,fd,rv; pid_t pid; int fds[2]; struct sigaction act; struct mypara pstru; char buf[BUF_SIZE]; if(argc!=2) { printf("Usage: %s <port>\n", argv[0]); exit(1); } //注册信号处理函数 act.sa_handler=read_childproc; sigemptyset(&act.sa_mask); act.sa_flags=0; state=sigaction(SIGCHLD,&act,0); serv_sock=socket(PF_INET,SOCK_STREAM,0); memset(&serv_adr,0,sizeof(serv_adr)); serv_adr.sin_family=AF_INET; serv_adr.sin_addr.s_addr=htonl(INADDR_ANY); serv_adr.sin_port=htons(atoi(argv[1])); if(bind(serv_sock,(struct sockaddr *)&serv_adr,sizeof(serv_adr))==-1) error_handling("bind()...error"); if(listen(serv_sock,5)==-1) error_handling("listen()...error"); //pipe(fds); //创建管道 socketpair(AF_UNIX, SOCK_STREAM, 0, fds); if (rv < 0) { printf("Call socketpair error, errno is %d\n", errno); return errno; } pid=fork(); pstru.tcp_sock = serv_sock; pstru.pip_sock = fds[1]; if(pid==0) /*子进程处理逻辑*/ { close(serv_sock);//子进程销毁服务端套接字，因为不需要使用 puts("work start..."); while(1) { fd = recv_fd(fds[0]); str_len = read(fds[0],buf,BUF_SIZE);//读 if (str_len > 0) puts(buf); if (fd > 0){ write(fd,buf,str_len); } } return 0; } for (j = 0; j < NUM_THREAD; j++) { pthread_create(&t_id[j],NULL,handle_clnt,(void*)&pstru); } for(k=0;k<NUM_THREAD;k++) pthread_join(t_id[k],NULL); return 0; } //每个线程执行的main入口函数 void * handle_clnt(void * arg) { struct mypara *pstru; pstru = (struct mypara *) arg; int serv_sock = pstru->tcp_sock; //tcp服务端描述符 int pip_sock = pstru->pip_sock; //管道描述符 int clnt_sock; struct sockaddr_in clnt_adr; socklen_t adr_sz; int str_len,i; char buf[BUF_SIZE];//接收数据 struct epoll_event *ep_events; struct epoll_event event; int epfd,event_cnt; epfd=epoll_create(EPOLL_SIZE); ep_events=malloc(sizeof(struct epoll_event)*EPOLL_SIZE); event.events=EPOLLIN; event.data.fd=serv_sock; epoll_ctl(epfd,EPOLL_CTL_ADD,serv_sock,&event); while(1) { event_cnt=epoll_wait(epfd,ep_events,EPOLL_SIZE,-1); if(event_cnt==-1) { puts("epoll_wait() error"); break; } puts("return epoll_wait"); for(i=0;i<event_cnt;i++) { if(ep_events[i].data.fd==serv_sock) { adr_sz=sizeof(clnt_adr); clnt_sock=accept(serv_sock,(struct sockaddr*)&clnt_adr,&adr_sz); event.events=EPOLLIN; event.data.fd=clnt_sock; epoll_ctl(epfd,EPOLL_CTL_ADD,clnt_sock,&event); printf("connected client: %d \n", clnt_sock); } else { str_len=read(ep_events[i].data.fd,buf,BUF_SIZE); if(str_len==0) { epoll_ctl(epfd,EPOLL_CTL_DEL,ep_events[i].data.fd,NULL); close(ep_events[i].data.fd); printf("closed client: %d \n", ep_events[i].data.fd); } else { write(pip_sock,buf,str_len);//写 send_fd(pip_sock, ep_events[i].data.fd); //write(ep_events[i].data.fd,buf,str_len); } } } } close(serv_sock); close(epfd); return NULL; } void read_childproc(int sig) { pid_t pid; int status; pid=waitpid(-1,&status,WNOHANG); printf("removed proc id: %d \n", pid); } void error_handling(char *msg) { fputs(msg,stderr); fputc('\n',stderr); exit(1); } int send_fd(int fd, int fd_to_send) { struct msghdr msg; struct iovec iov[1]; char buf[100]; union { //保证cmsghdr和msg_control对齐 struct cmsghdr cm; char control[CMSG_SPACE(sizeof(int))]; } control_un; struct cmsghdr *pcmsg; int ret; //udp需要,tcp无视 msg.msg_name = NULL; msg.msg_namelen = 0; iov[0].iov_base = buf; iov[0].iov_len = 100; msg.msg_iov = iov; msg.msg_iovlen = 1; //设置缓冲区和长度 msg.msg_control = control_un.control; msg.msg_controllen = sizeof(control_un.control); //直接通过CMSG_FIRSTHDR取得附属数据 pcmsg = CMSG_FIRSTHDR(&msg); pcmsg->cmsg_len = CMSG_LEN(sizeof(int)); pcmsg->cmsg_level = SOL_SOCKET; pcmsg->cmsg_type = SCM_RIGHTS; //指明发送的是描述符 *((int*)CMSG_DATA(pcmsg)) == fd_to_send; //把描述符写入辅助数据 ret = sendmsg(fd, &msg, 0); if(ret < 0) { printf("sendmsg error, errno is %d\n", errno); printf("%s\n",strerror(errno)); printf ("ret = %d, filedescriptor = %d\n", ret, fd_to_send); return errno; } return 0; } int recv_fd(int fd) { struct msghdr msg; struct iovec iov[1]; char buf[100]; int ret,recvfd; union { //对齐 struct cmsghdr cm; char control[CMSG_SPACE(sizeof(int))]; } control_un; struct cmsghdr * pcmsg; msg.msg_name = NULL; msg.msg_namelen = 0; //设置数据缓冲区 iov[0].iov_base = buf; iov[0].iov_len = 100; msg.msg_iov = iov; msg.msg_iovlen = 1; //设置辅助数据缓冲区和长度 msg.msg_control = control_un.control; msg.msg_controllen = sizeof(control_un.control); //接收 ret = recvmsg(fd , &msg, 0); if( ret <= 0 ) { return ret; } //检查是否收到了辅助数据，以及长度 if((pcmsg = CMSG_FIRSTHDR(&msg) ) != NULL && ( pcmsg->cmsg_len == CMSG_LEN(sizeof(int)))) { if ( pcmsg->cmsg_level != SOL_SOCKET ) { printf("cmsg_leval is not SOL_SOCKET\n"); return -1; } if ( pcmsg->cmsg_type != SCM_RIGHTS ) { printf ( "cmsg_type is not SCM_RIGHTS" ); return -1; } //这就是我们接收的描述符 recvfd = *((int*)CMSG_DATA(pcmsg)); return recvfd; } return -1; }

include

int main(int argc, char argv[]) { char file_desc = "/tmp/test.txt"; int fd = open(file_desc, O_RDWR);

if (fd < 0) { perror("Failed to open file"); return 1; } char data[1024]; write(fd, "Hello, World!", sizeof(data)); printf("Data written: %s\n", data); close(fd); return 0;

} ```

在这个示例中，我们首先创建了一个文件描述符/tmp/test.txt，然后使用open()函数打开了这个文件描述符。然后，我们使用write()函数向文件描述符中写入了一个字符串"Hello, World!"。最后，我们关闭了文件描述符。

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