实验五--进程间通信

实验五 进程间通信UNIX/LINUX系统的进程间通信机构（IPC）允许在任意进程间大批量地交换数据。本实验的目的是了解和熟悉LINUX支持的信号机制、管道机制、消息队列通信机制及共享存储区机制。5.1信号机制实验（一）【实验目的】1了解什么是信号。2熟悉LINUX系统中进程之间软中断通信的基本原理。【实验原理】利用signal来实现发送信号和接受信号的原理【实验内容】1编写一段程序，使用系统调用fork( )创建两个子进程，再用系统调用signal( )让父进程捕捉键盘上来的中断信号（即按ctrl+c键），当捕捉到中断信号后，父进程用系统调用kill( )向两个子进程发出信号，子进程捕捉到父进程发来的信号后，分别输出下列信息后终止： Child process 1 is killed by parent!Child process 2 is killed by parent!父进程等待两个子进程终止后，输出以下信息后终止： Parent process is killed! # include# include# includeint wait_mark;void waiting(),stop();void main() int p1, p2;signal(SIGINT,stop);while(p1=fork()=-1);if(p10)/*在父进程中*/ while(p2=fork()= =-1); If(p20)/*在父进程中*/ wait_mark=1; waiting(0); kill(p1,10); kill(p2,12); wait( ); wait( ); printf(“parent process is killed!n”); exit(0); else/*在子进程2中*/ wait_mark=1;signal(12,stop);waiting();lockf(1,1,0);printf(“child process 2 is killed by parent!n”);lockf(1,0,0);exit(0); else/*在子进程1中*/ wait_mark=1; signal(10,stop); waiting(); lockf(1,1,0); printf(“child process 1 is killed by parent!n”); lockf(1,0,0); exit(0);void waiting() while(wait_mark!=0);void stop() wait_mark=0;实验要求： 运行程序并分析结果。 如果把signal(SIGINT,stop)放在号和号位置，结果会怎样并分析原因。 该程序段前面部分用了两个wait(0),为什么？ 该程序段中每个进程退出时都用了语句exit(0),为什么？5.2信号机制实验（二）【实验目的】学习signal的函数的使用【实验原理】利用signal的函数的机制来实习我们发送截获信号的功能【实验内容】修改上面的程序，增加语句signal(SIGINT,SIG_IGN)和语句signal(SIGQUIT,SIG_IGN)，再观察程序执行时屏幕上出现的现象，并分析其原因。# include# include# includeint pid1, pid2;int EndFlag=0;pf1=0;pf2=0;void IntDelete() kill(pid1,10); kill(pid2,12);EndFlag=1;void Int1() printf(“child process 1 is killed by parent !n”); exit(0);void Int2() printf(“child process 2 is killed by parent !n”); exit(0);main() int exitcode; signal(SIGINT,SIG_IGN); signal(SIGQUIT,SIG_IGN);while(pid1=fork()=-1); if(pid1=0) signal(SIGUSR1,Int1);signal(SIGINT,SIG_IGN);pause();exit(0); else while(pid2=fork()= =-1); if(pid2=0) signal(SIGUSR2,Int2);signal(SIGINT,SIG_IGN);pause();exit(0); else signal(SIGINT,IntDelete); waitpid(-1,&exitcode,0);/*等待任何子进程中断或结束*/ printf(“parent process is killed n”); exit(0); 实验要求：运行程序并分析结果。司机售票员问题（选做题）编程用fork()创建一个子进程代表售票员，司机在父进程中，再用系统调用signal()让父进程（司机）捕捉来自子进程（售票员）发出的中断信号，让子进程（售票员）捕捉来自（司机）发出的中断信号，以实现进程间的同步运行。5.3管道通信实验（一）【实验目的】1、了解什么是管道2、熟悉UNIX/LINUX支持的管道通信方式【实验内容】编写程序实现进程的管道通信。用系统调用pipe( )建立一管道，二个子进程P1和P2分别向管道各写一句话： Child 1 is sending a message! Child 2 is sending a message!父进程从管道中读出二个来自子进程的信息并显示（要求先接收P1，后P2）。参考程序#include #include #include int pid1,pid2;main( ) int fd2;char outpipe100,inpipe100;pipe(fd); /*创建一个管道*/while (pid1=fork( )= =-1);if(pid1= =0)lockf(fd1,1,0); sprintf(outpipe,child 1 process is sending message!); /*把串放入数组outpipe中*/ write(fd1,outpipe,50); /*向管道写长为50字节的串*/ sleep(5); /*自我阻塞5秒*/ lockf(fd1,0,0); exit(0);elsewhile(pid2=fork( )= =-1); if(pid2= =0) lockf(fd1,1,0); /*互斥*/ sprintf(outpipe,child 2 process is sending message!); write(fd1,outpipe,50); sleep(5);lockf(fd1,0,0); exit(0); else wait(0); /*同步*/ read(fd0,inpipe,50); /*从管道中读长为50字节的串*/ printf(%s/n,inpipe); wait(0); read(fd0,inpipe,50); printf(%s/n,inpipe); exit(0); 五、运行结果 延迟5秒后显示child 1 process is sending message! 再延迟5秒child 2 process is sending message!5.4管道通信实验（二）【实验目的】1、掌握有名管道的创建和读写方式2、熟悉UNIX/LINUX支持的有名管道通信方式【实验内容】1. 创建有名管道2. 本进程执行循环等待数据被写入到管道中并读有名管道3. 打开有名管道并写数据到名管道参考代码：/read_fifo.c#include #include #include #include #include #include #include #define BUFFER_SIZE1024int main(int argc, char *argv) int fd; if (argc 2) fprintf(stdout, Usage: %s n, argv0); exit(1); /int open(const char *path, int oflag, .); if (fd = open(argv1, O_RDONLY) 0) fprintf(stderr, open fifo %s for reading failed: %sn, argv1, strerror(errno); exit(1); fprintf(stdout, open fifo %s for reading successed.n, argv0); char bufferBUFFER_SIZE; ssize_t n; while (1) again: /ssize_t read(int fd, void *buf, size_t count); if (n = read(fd, buffer, BUFFER_SIZE) 0) if (errno = EINTR) goto again; else fprintf(stderr, read failed on %s: %sn, argv1, strerror(errno);exit(1); else if (n = 0) fprintf(stderr, peer closed fifo.n); break; else buffern = 0; fprintf(stdout, read %d bytes from fifo: %sn, n, buffer); return 0;/ write_fifo.c#include #include #include #include #include #include #include #include #define BUFFER_SIZE1024void signal_handler(int s);int main(int argc, char *argv) int fd; if (argc 2) fprintf(stdout, Usage: %s n, argv0); exit(1); signal(SIGPIPE, signal_handler); /int open(const char *path, int oflag, .); if (fd = open(argv1, O_WRONLY) 0) fprintf(stderr, open fifo %s for writting failed: %sn, argv1, strerror(errno); exit(1); fprintf(stdout, open fifo %s for writting successed.n, argv0); char bufferBUFFER_SIZE; ssize_t n; /char *fgets(char *s, int size, FILE * stream); while (fgets(buffer, BUFFER_SIZE, stdin) again: /ssize_t write(int fd, const void *buf, size_t count); if (n = write(fd, buffer, strlen(buffer) 0) if (errno = EINTR) goto again; else fprintf(stderr, write() failed on fifo: %sn, strerror(errno);/ FIXME:break; return 0;void signal_handler(int s) fprintf(stdout, Caught signal %dn, s);/ create_fifo.c#include #include #include #include #include int main(int argc, char *argv) if (argc 2) fprintf(stdout, Usage: %s n, argv0); exit(1); /int mkfifo(const char *path, mode_t mode); if (mkfifo(argv1, 0644) 0) fprintf(stderr, mkfifo() failed: %sn, strerror(errno); exit(1); return 0;5.5共享内存通信实验【实验目的】1、掌握共享内存的创建和读写方式2、熟悉UNIX/LINUX支持的共享内存通信方式【实验内容】1. 创建共享内存2. 写入到共享内存3. 读数据从共享内存代码参考：/write.c#include #include #include #include #include #include #include #include #include #define MAPPED_FILENAME/tmp/test.mmap.1int main(int argc, char *argv) int fd; if (argc 2) fprintf(stdout, Usage: %s n, argv0); exit(1); / XXX: step 1, open file, get a fd /int open(const char *pathname, int flags, mode_t mode); if (fd = open(argv1, O_RDWR | O_CREAT | O_EXCL, 0644) 0) if (errno = EEXIST) fprintf(stderr, Fatal error: The target mapped file existed, exit.n); else fprintf(stderr, Error: open file failed: (errno = %d)%sn, errno, strerror(errno); exit(1); off_t offset; offset = 1024; / XXX: step 2, create a hole file /off_t lseek(int fildes, off_t offset, int whence); if (lseek(fd, offset, SEEK_SET) = (off_t) - 1) fprintf(stderr, lseek() failed: %sn, strerror(errno); /FIXME: unlink the file close(fd); exit(1); ssize_t n; /ssize_t write(int fd, const void *buf, size_t count); if (n = write(fd, , 1) 0) fprintf(stderr, write() failed: %sn, strerror(errno); exit(1); /* * On success, mmap returns a pointer to the mapped area. On error, the value MAP_FAILED (that is, (void*) -1) is returned, and errno is set appropriately. On success, munmap returns 0, on failure -1, and errno is set (probably to EINVAL). */* PROT_EXEC Pages may be executed. PROT_READ Pages may be read. PROT_WRITE Pages may be written. PROT_NONE Pages may not be accessed.*/ void *p; / XXX: step 3, mmap(), get a pointer /void * mmap(void *start, size_t length, int prot , int flags, int fd, off_t offset); if (p = mmap(NULL, 1024, PROT_WRITE, MAP_SHARED, fd, 0) = MAP_FAILED) fprintf(stderr, mmap() failed: %sn, strerror(errno); close(fd); exit(1); close(fd); fprintf(stdout, mapped file to memory, size = %dn, 1024); / XXX: step 4, read/write on shared memory char *banner = hello world.; /void *memcpy(void *dest, const void *src, size_t n); memcpy(p + 256, banner, strlen(banner); / XXX: step 5, munmap(); /int munmap(void *start, size_t length); pause(); /close(fd); return 0;/ read.c#include #include #include #include #include #include #include #include #include #define MAPPED_FILENAME/tmp/test.mmap.1#define BUFFER_SIZE1024int main(int argc, char *argv) int fd; if (argc 2) fprintf(stdout, Usage: %s n, argv0); exit(1); / XXX: step 1, open file, get a fd /int open(const char *pathname, int flags, mode_t mode); if (fd = open(argv1, O_RDWR) 0) fprintf(stderr, Error: open file failed: (errno = %d)%sn, errno, strerror(errno); exit(1); #if 0 off_t offset; offset = 1024; / XXX: step 2, create a hole file /off_t lseek(int fildes, off_t offset, int whence); if (lseek(fd, offset, SEEK_SET) = (off_t) - 1) fprintf(stderr, lseek() failed: %sn, strerror(errno); /FIXME: unlink the file close(fd); exit(1); ssize_t n; /ssize_t write(int fd, const void *buf, size_t count); if (n = write(fd, , 1) 0) fprintf(stderr, write() failed: %sn, strerror(errno); exit(1); #endif /* * On success, mmap returns a pointer to the mapped area. On error, the value MAP_FAILED (that is, (void*) -1) is returned, and errno is set appropriately. On success, munmap returns 0, on failure -1, and errno is set (probably to EINVAL). */* PROT_EXEC Pages may be executed. PROT_READ Pages may be read. PROT_WRITE Pages may be written. PROT_NONE Pages may not be accessed.*/ void *p; / XXX: step 3, mmap(), get a pointer /void * mmap(void *start, size_t length, int prot , int flags, int fd, off_t offset); if (p = mmap(NULL, 1024, PROT_WRITE, MAP_SHARED, fd, 0) = MAP_FAILED) fprintf(stderr, mmap() failed: %sn, strerror(errno); close(fd); exit(1); close(fd); fprintf(stdout, mapped file to memory, size = %dn, 1024); char bufferBUFFER_SIZE; / XXX: step 4, read/write on shared memory /void *memcpy(void *dest, const void *src, size_t n); memcpy(buffer, p+256, 32); fprintf(stdout, %sn, buffer); / XXX: step 5, munmap(); /int munmap(void *start, size_t length); /close(fd); return 0;5.6用消息队列编写一个客户端服务器通信的程序【实验目的】通过此实验，学员可以熟悉消息队列的概念，并能够用消息队列编写一个客户端服务器通信的程序。【实验原理】本实验需要用消息队列设计一个简易的双人聊天程序（一个服务器，两个客户端）。消息队列重点在于消息类型的匹配，客户端和服务端的“通信协议”的设计。设计思想如下：服务器端：接受客户端发来的任何信息，并根据其消息类型，转发给对应的客户端。同时，检测是否有退出标志，有则给所有的客户端发送退出标志，等待10s后，确定客户端都退出后，删除消息队列，释放空间，并退出。客户端：A和B，A给B发送信息，先发给服务器，由服务器根据自定义协议转发该消息给B。同时B接受到消息后，经由服务器给A一个回执信息，以此形成简易的聊天模式。【实验方法】编写服务器端程序：#define KEY_MSG 0x101 /使用共有的IPC key#define MSGSIZE 128#include #include #include #include #include main() int msgid; struct msgbuf /定义消息结构体：消息类型和消息数据 long mtype; char mtext128; buf1, buf2; msgid = msgget( KEY_MSG, IPC_CREAT|0666 ); while( 1 ) /无限循环，退出标志则会break msgrcv( msgid, &buf1, MSGSIZE, 1L, 0 ); /接受客户端1的消息printf( Receive client1 message: %sn, buf1.mtext ); /打印收到的消息if( buf1.mtext0 = x | buf1.mtext0 = X ) /若是退出标志，则给2个客户端都发退出信息 strcpy( buf1.mtext, x ); buf1.mtype = 3L; msgsnd( msgid, &buf1, MSGSIZE, 0 ); buf1.mtype = 4L; msgsnd( msgid, &buf1, MSGSIZE, 0 ); break; buf1.mtype = 4L;msgsnd( msgid, &buf1, MSGSIZE, 0 ); /将客户端1的消息转发给客户端2 msgrcv( msgid, &buf2, MSGSIZE, 2L, 0 ); /接受客户端2的消息printf( Receive client2 message: %sn, buf2.mtext ); /打印收到的消息if( buf2.mtext0 = x | buf2.mtext0 = X )/若是退出标志，则给2个客户端发退出信息 strcpy( buf2.mtext, x ); buf2.mtype = 3L; msgsnd( msgid, &buf2, MSGSIZE, 0 ); buf2.mtype = 4L; msgsnd( msgid, &buf2, MSGSIZE, 0 ); break; buf2.mtype = 3L;msgsnd( msgid, &buf2, MSGSIZE, 0 ); /将客户端2的消息转发给客户端1 sleep(5); /若退出，则先等待，以确保客户端程序退出 msgctl( msgid, IPC_RMID, NULL ); /删除消息队列，释放空间 exit(0);客户端1：#define KEY_MSG 0x101#define MSGSIZE 128#include #include #include #include #include main() int msgid; struct msgbuf long mtype; char mtext128; buf1, buf2; msgid = msgget( KEY_MSG, 0666 ); while( 1 ) printf( input the msg to client2: ); gets( buf1.mtext ); buf1.mtype = 1L; msgsnd( msgid, &buf1, MSGSIZE, 0 ); /客户端1获取消息并发往服务器sleep(1); /等待一秒，以确保客户端2已经收到并发了回执 msgrcv( msgid, &buf2, MSGSIZE, 3L, 0 ); /准备从客户端2获取回执消息 if( buf2.mtext0 = x | buf2.mtext0 = X ) printf( client1 will quit!n ); break; p