使用带有整数和字符串的 FIFO(管道)时出现问题

Question

我的程序中遇到了一个问题，我需要将字符串从客户端带到服务器，然后服务器将使用该字符串来创建私有FIFO。但是，当我在客户端上提示时键入名称，然后尝试在服务器上继续时，它出错说：不存在文件或目录。

另外，我不明白如何将整数从服务器移动到客户端，因为 write（） 方法不起作用（似乎仅适用于字符和字符串）。

客户端：

main (void)
{
  int fda;  // to write to server
  int fdb;  // to read response from server
  int mem_req[1];   // buffer holds a #
  char outchar[7];  // server puts string here
  char pfifo_name[10];
  memset(mem_req,0,1); 
  memset(outchar,0,7); 
  memset(pfifo_name,0,10);
  printf("nClient: Please enter a private FIFO name (less than 10 chars): ");
  scanf("%s", &pfifo_name);
  printf("nClient: Please enter a memory request number: ");
  scanf("%d", &mem_req);
  if((fda=open("FIFO1", O_WRONLY))<0)
     printf("cant open fifo to write");
  if((fdb=open(pfifo_name, O_RDONLY))<0)
     printf("cant open fifo to read");


  write(fda, mem_req, 1);
  write(fda, pfifo_name, 10);
  printf("nClient: Pfifo and memory request sent to server ");
  read(fdb, outchar, 7);
  printf("nClient: received from server %s", outchar);
  close(fda);
  close(fdb);
  printf ("nall done!n");

服务器端：

     main (void)
{
  int fda;  // to read from client
  int fdb;  // to write to client
  int finish;   // lets me know that client is done
  int i;    // because C needs this defined as int
  int fr_size; // frame size for memory management
  int temp_mem;
  int n_frame = 0;
  int o_frame = 0;
  int n_byte = 0;
  int o_byte = 0;
  int fr_num = 0;
  int byte_num;
  char mem_req[1];  // buffer holds a character
  char outchar[7];  // server puts string here
  char pfifo_name[10]; //client provides server a private fifo name
  memset(mem_req,0,1); 
  memset(outchar,0,7); 
  memset(pfifo_name,0,10);
  printf("nServer: Please enter a desired frame(page) size: ");
  scanf("%d", &fr_size);
  read(fda, pfifo_name, 10);
  /* Create the fifos and open them  */
  if ((mkfifo("FIFO1",0666)<0 && errno != EEXIST))
    {
    perror("cant create FIFO1");
    exit(-1);
    }
   if ((mkfifo(pfifo_name,0666)<0 && errno != EEXIST))
    {
    perror("cant create private fifo");
    exit(-1);
    }
  if((fda=open("FIFO1", O_RDONLY))<0)
     printf("cant open fifo to read");
  if((fdb=open(pfifo_name, O_WRONLY))<0)
     printf("cant open fifo to write");

  printf("nServer: just got memeory request: ,%d", mem_req[0]);
  temp_mem = mem_req[0];
  n_frame = temp_mem/fr_size; // number of frames required for job
  n_byte = temp_mem - (n_frame * fr_size); // ending byte location
  write(fdb, &o_frame, sizeof(o_frame)); // output frame start location
  printf("nServer: Frame start location sent");
  write(fdb, &o_byte, sizeof(o_byte));
  printf("nServer: Byte start location sent");
  write(fdb, &n_frame, sizeof(n_frame));
  printf("nServer: Frame end location sent");
  write (fdb, &n_byte, sizeof(n_byte));
  printf("nServer: Byte end location sent");
  finish=read(fda, pfifo_name, 10);     //read the character

当编译器到达服务器上的 mkfifo（pfifo_name，0666）<0 时，它会出错：

"无法创建私有FIFO：不存在此类文件或目录"

我还收到来自服务器上所有 4 个 write 语句的错误（尝试通过管道传递整数，但它不起作用）

Answer 1

在服务器中：

read(fda, pfifo_name, 10);

此操作失败fda因为它不包含有效的文件描述符，因为它从未初始化过。

结果，没有任何东西被读入pfifo_name，所以它只保存0个字节（因为之前对memset的调用），即一个空字符串。然后，将此传递给 open ，这会尝试打开一个名称为空的文件，该文件无效。