读/写:非法查找 - 客户端-服务器C++

Question

我在stackoverflow客户端-服务器代码（使用命名管道）上找到了它，并对其进行了修改，以允许客户端在while循环中发送消息。虽然我从服务器收到消息，但我在读/写时收到"非法搜索"，我不确定这是否是一个严重的错误，如果这里有什么东西真的很糟糕？

服务器.cpp

#include <fcntl.h>
#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
int main()
{
   int client_to_server;
   char *myfifo = "/tmp/client_to_server_fifo";
   int server_to_client;
   char *myfifo2 = "/tmp/server_to_client_fifo";
   char buf[BUFSIZ];
   /* create the FIFO (named pipe) */
   mkfifo(myfifo, 0666);
   mkfifo(myfifo2, 0666);
   /* open, read, and display the message from the FIFO */
   client_to_server = open(myfifo, O_RDONLY);
   server_to_client = open(myfifo2, O_WRONLY);
   printf("Server ON.n");
   while (1)
   {
      read(client_to_server, buf, BUFSIZ);
      if (strcmp("exit",buf)==0)
      {
         printf("Server OFF.n");
         break;
      }
      else if (strcmp("",buf)!=0)
      {
         printf("Received: %sn", buf);
         printf("Sending back...n");
         write(server_to_client,buf,BUFSIZ);
      }
      /* clean buf from any data */
      memset(buf, 0, sizeof(buf));
   }
   close(client_to_server);
   close(server_to_client);
   unlink(myfifo);
   unlink(myfifo2);
   return 0;
}

客户端.cpp

#include <stdio.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
int main()
{
   int client_to_server;
   char *myfifo = "/tmp/client_to_server_fifo";
   int server_to_client;
   char *myfifo2 = "/tmp/server_to_client_fifo";
   char str[BUFSIZ];

   //printf("Input message to serwer: ");
   //scanf("%s", str);

   /* write str to the FIFO */
   client_to_server = open(myfifo, O_WRONLY);
   server_to_client = open(myfifo2, O_RDONLY);
while(true)
{
   printf("> "); 
   scanf("%s", str);
   write(client_to_server, str, sizeof(str));
   perror("Write:"); //Very crude error check
   read(server_to_client,str,sizeof(str));
   perror("Read:"); // Very crude error check
   printf("From  server: %sn",str);
}
   close(client_to_server);
   close(server_to_client);
   /* remove the FIFO */
   return 0;
}

示例输出：

客户 ：

> hello, server!
Write:: Success
Read:: Illegal seek
From  server: hello,
Write:: Illegal seek
Read:: Illegal seek
> From  server: server!
> its client here!
Write:: Illegal seek
Read:: Illegal seek
From  server: its
Write:: Illegal seek
Read:: Illegal seek
> From  server: client
Write:: Illegal seek
Read:: Illegal seek
> From  server: here!
> > hello, server!
// and so on ...

服务器 ：

Server ON.
Received: hello,
Sending back...
Received: server!
Sending back...
Received: its
Sending back...
Received: client
Sending back...
Received: here!
Sending back...
Received: >
Sending back...
Received: hello,
Sending back...
Received: server!
Sending back...
Received: Write::
Sending back...
Received: Success
Sending back...
Received: Read::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: From
Sending back...
Received: server:
Sending back...
Received: hello,
Sending back...
Received: Write::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: Read::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: >
Sending back...
Received: From
Sending back...
Received: server:
Sending back...
Received: server!
Sending back...
Received: >
Sending back...
Received: its
Sending back...
Received: client
Sending back...
Received: here!
Sending back...
Received: Write::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: Read::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: From
Sending back...
Received: server:
Sending back...
Received: its
Sending back...
Received: Write::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: Read::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: >
Sending back...
Received: From
Sending back...
Received: server:
Sending back...
Received: client
Sending back...
Received: Write::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: Read::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: >
Sending back...
Received: From
Sending back...
Received: server:
Sending back...
Received: here!
Sending back...
Received: >
Sending back...

Answer 1

如果没有

错误，请不要调用perror。

您需要先检查上一个函数调用是否失败，然后才能调用perror否则当实际没有发生错误时，您将收到无意义的错误消息。如果函数没有失败，则不需要将errno设置为任何特定内容。