Question

计划行为：

服务器：

创建FIFO
听取客户写信，阻止读取内容。
如果读取了某些内容，则会提示“写入客户端”消息。
重复...

客户端：

要写入服务器的提示消息。
写完后，收听传入消息。
如果阅读了某些内容，请提示回复邮件。
重复...

================================的问题 ======= ============================

程序确实进行通信，但有时呼叫READ将无法捕获来自其他程序的WRITE呼叫。

=============================================== =========================

服务器代码：

#include <fcntl.h>
#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>

#define SERVER_FIFO_FILE "/lab7_server_fifo"
#define CLIENT_FIFO_FILE "/lab7_client_fifo"

#define PERM 0666

int main(int argc, char** argv)
{
  int s_read = 0;
  int s_write = 0;

  int exit = 0;
  int listening = 1;
  int writing = 0;

  char* w_buffer = NULL;
  size_t w_buffer_len = 0;
  char r_buffer[BUFSIZ];

  char* home = getenv("HOME");
  char SERVER_FIFO[100];
  char CLIENT_FIFO[100];
  strcpy(SERVER_FIFO,home);
  strcat(SERVER_FIFO, SERVER_FIFO_FILE);
  strcpy(CLIENT_FIFO,home);
  strcat(CLIENT_FIFO, CLIENT_FIFO_FILE);

  mkfifo(SERVER_FIFO, PERM);
  mkfifo(CLIENT_FIFO, PERM);

  s_read = open(SERVER_FIFO, O_RDONLY | O_NONBLOCK);
  s_write = open(CLIENT_FIFO, O_WRONLY | O_NONBLOCK);

  while (!exit)
  {
     if (writing)
     {
        printf(">>>");
        getline(&w_buffer,&w_buffer_len,stdin);
        if (strcmp("exit",w_buffer)==0)
        {
          exit = 1;
        }
        else
        {
          write(s_write,w_buffer,w_buffer_len);
          writing = 0;
          listening = 1;
        }
     }
     else
     {
        if (listening)
        {
           printf("listening...\n");
           listening = 0;
        }
        read(s_read, r_buffer, BUFSIZ);
        if (strlen(r_buffer) != 0)
        {
           if (strcmp(r_buffer,"exit") == 0)
           {
              exit = 1;
           }
           else
           {
              printf("%s",r_buffer);
              writing = 1;
           }
        }
     }
     memset(r_buffer, 0, sizeof(r_buffer));
  }
  close(s_read);
  close(s_write);

  remove(SERVER_FIFO);
  remove(CLIENT_FIFO);

  return 0;
}

客户代码：

#include <fcntl.h>
#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>

#define SERVER_FIFO_FILE "/lab7_server_fifo"
#define CLIENT_FIFO_FILE "/lab7_client_fifo"

int main(int argc, char** argv)
{
   int c_read = 0;
   int c_write = 0;

   int exit = 0;
   int listening = 0;
   int writing = 1;

   char* w_buffer = NULL;
   size_t w_buffer_len = 0;
   char r_buffer[BUFSIZ];

   char* home = getenv("HOME");
   char SERVER_FIFO[100];
   char CLIENT_FIFO[100];
   strcpy(SERVER_FIFO,home);
   strcat(SERVER_FIFO, SERVER_FIFO_FILE);
   strcpy(CLIENT_FIFO,home);
   strcat(CLIENT_FIFO, CLIENT_FIFO_FILE);

   c_write = open(SERVER_FIFO, O_WRONLY | O_NONBLOCK);
   c_read = open(CLIENT_FIFO, O_RDONLY | O_NONBLOCK);

   while (!exit)
   {
      if (writing)
      {
         printf(">>>");
         getline(&w_buffer,&w_buffer_len,stdin);
         if (strcmp("exit",w_buffer)==0)
         {
           exit = 1;
         }
         else
         {
            write(c_write,w_buffer,w_buffer_len);
            writing = 0;
            listening = 1;
         }
      }
      else
      {
         if (listening)
         {
            printf("listening...\n");
            listening = 0;
         }
         read(c_read, r_buffer, BUFSIZ);
         if (strlen(r_buffer) != 0)
         {
            printf("%s",r_buffer);
            writing = 1;
         }
      }
      memset(r_buffer, 0, sizeof(r_buffer));
   }
   close(c_read);
   close(c_write);

   return 0;
}

当前输出：

服务器：

listening...
hello
>>>hi
listening...

客户端：

>>>hello
listening...
hi
>>how are you
listening...

问题：服务器未收到来自服务器的消息“你好吗”。客户进入了聆听阶段，导致程序陷入聆听的循环中。

已解决我所要做的就是添加标志O_SYNC以写入服务器和客户端，这样它就会自动刷新到磁盘，导致它变慢，这样读取就会有足够的时间来捕获电话。

Linux FIFO聊天程序 - 读/写问题

0 个答案: