在单个 main() 函数中,因此需要信号处理。使用Posix消息队列IPC机制,可以忽略优先级和其他链表消息,实现场景:
客户端:敲敲
服务器:谁在那儿
客户:pilcrow
服务器:pilcrow,非常感谢。
客户端:退出
所有进程终止
stdin->POSIX MsgQ 客户端发送“knock Knock”到服务器->服务器比较字符串并将“who's there”发送回客户端
我得到的是:
客户端:敲敲
服务器:谁在那里?
客户:pilcrow
枕头
客户端:退出
退出
第一轮成功地给了我正确的结果。从第二轮开始,客户端在控制台上输出相同的输入。
请帮忙。请记住使用 gcc -lrt 链接 mq_function。
下面是我的代码,
#include <mqueue.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <sys/types.h>
#define MSG_SIZE 100 //max size of msg
#define MAX_MSG 1 //max # of msg
#define FILE_MODE (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)
volatile sig_atomic_t mqflag; /* set nonzero by signal handler */
static void sig_usr1(int);
sigset_t zeromask, newmask, oldmask;
int main(int argc, char **argv) {
int c,flags;/* for getopt() */
pid_t child_pid;
mqd_t msgq_id;
struct mq_attr attr;
struct sigevent sigev;
char *buff_forward,*buff_backward;
flags=O_RDWR | O_CREAT;
attr.mq_msgsize=MSG_SIZE;
attr.mq_maxmsg=MAX_MSG;
buff_forward=malloc(attr.mq_msgsize);
buff_backward=malloc(attr.mq_msgsize);
while ((c= getopt(argc, argv, "e")) != -1) {
switch (c) {
case 'e': /* create the queue exclusive */
flags|= O_EXCL;
break;
}
}
if (optind!=argc-1){
printf("usage: [-e] <name>");
exit(1);
}
msgq_id = mq_open(argv[optind],flags,FILE_MODE,&attr);
/* producing the message */
mq_getattr(msgq_id, &attr) ;
printf("Queue \"%s\":\n\t- stores at most %ld messages\n\t- "
"large at most %ld bytes each\n\t- currently holds %ld messages\n",
argv[optind], attr.mq_maxmsg, attr.mq_msgsize, attr.mq_curmsgs);
sigemptyset(&zeromask); /* no signals blocked */
sigemptyset(&newmask);
sigemptyset(&oldmask);
sigaddset(&newmask, SIGUSR1);
/* establish signal handler, enable notification */
signal(SIGUSR1, sig_usr1);
sigev.sigev_notify = SIGEV_SIGNAL;
sigev.sigev_signo = SIGUSR1;
sigprocmask(SIG_BLOCK, &newmask, &oldmask);/* block SIGUSR1 */
if ((child_pid=fork())==0){
for (; ; ) {
while (mqflag == 0)
sigsuspend(&zeromask);
mqflag =0; /* reset flag */
msgq_id=mq_open(argv[optind],O_RDONLY);
mq_receive(msgq_id, buff_forward, attr.mq_msgsize, NULL);
mq_close(msgq_id);
if (strcasecmp ("Knock Knock",buff_forward)==0){
strcpy(buff_backward,"Server:Who's there?");
}
else if(strcasecmp ("pilcrow", buff_forward)==0){
strcpy(buff_backward,"Server:Pilcrow,thanks a lot!");
}
else if(strcasecmp ("Exit",buff_forward)==0){
kill(getppid(),SIGTERM);
exit(0);
}
msgq_id=mq_open(argv[optind],O_WRONLY);
mq_send(msgq_id,buff_backward,MSG_SIZE,NULL);
mq_close(msgq_id);
mq_notify(msgq_id, &sigev); /* reregister */
}
sigprocmask(SIG_UNBLOCK, &newmask, NULL); /* unblock SIGUSR1 */
exit(0);
}
else if(child_pid>0){
for(;;){
printf("client:");
gets(buff_forward);
msgq_id=mq_open(argv[optind],O_WRONLY);
mq_send(msgq_id,buff_forward,MSG_SIZE,NULL);
mq_close(msgq_id);
mq_notify(msgq_id, &sigev);
while(mqflag==0)
sigsuspend(&zeromask);
mqflag==0;
msgq_id=mq_open(argv[optind],O_RDONLY);
mq_receive(msgq_id, buff_backward, attr.mq_msgsize, NULL);
printf("%s\n",buff_backward);
mq_close(msgq_id);
}
sigprocmask(SIG_UNBLOCK, &newmask, NULL); /* unblock SIGUSR1 */
exit(0);
}
return (EXIT_SUCCESS);
}
static void sig_usr1(int signo) {
mqflag = 1;
sigprocmask(SIG_BLOCK, &newmask, &oldmask);
return;
}
最佳答案
子进程在调用 mq_notify
之前调用 sigsuspend
(因为 mq_flag
隐式初始化为零,并且检查在通知之前中断被不当执行)。它永远无法按预期被唤醒。
将 mq_flag
初始化为 1 以查看差异。然后重构。
已更新
OP大大改变了代码,所以我也改变了这个答案。
关于c - 帮助:wrong behavior code:client-server IPC signal handling on POSIX Message Queue UNIX C programming,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/6352765/