c - 写入和读取 - 套接字 AF_UNIX

Question

我正在为大学做一个项目。需要编写一个套接字的代码，一个服务器和一个客户端通过这个套接字进行通话。消息是这样的:

typedef struct {
  /** message type */
    char type;           
  /** message length in byte */
    unsigned int length; 
  /** message buffer */
    char *buffer;        
  } message_t; 

我写了 Socket 的代码，现在我遇到了两个函数的问题:sendMessage 和 receiveMessage

    /** read a message from the socket --- properly split the message and put it in the struct message_t 
 *  \param  sc  file descriptor of the socket
 *  \param msg  
 *
 *  \retval lung  length of the buffer read, if it's OK 
 *  \retval  -1   if there are errors (set errno)
 *                
 *      
 */
int receiveMessage(int sc, message_t * msg) {

  int lung;

  lung = read(sc, &(msg->type), sizeof(char));
  if(lung == 0) 
    return -1;
  if(lung == -1)
    return -1;

  lung = read(sc, &(msg->length), sizeof(unsigned int));
  if(lung == 0)
    return -1;
  if(lung == -1)
    return -1;

  if(msg->length > 0) {

    msg->buffer = malloc (sizeof(char)*msg->length);

    lung = read(sc, &(msg->buffer), sizeof(char)*msg->length);
    if(lung == 0)
      return -1;
    if(lung == -1)
      return -1;
  }
  return lung;
   }

这是发送消息

/** write a message on the socket --- should send only significant byte of the buffer    (msg->length byte) --  must use only 1 write
 *   \param  sc file descriptor of the socket
 *   \param msg address of the struct 
 *   
 *   \retval  n    no. of char sent (if its OK)
 *   \retval -1   if there are errores (set errno)
 *                  
 *                  
 */
int sendMessage(int sc, message_t *msg) {

  int n,lung;

  lung = sizeof(unsigned int) + sizeof(char) + (sizeof(char)*msg->length);

  record = malloc (lung);

  sprintf(record,"%c%u%s",msg->type,msg->length,msg->buffer);

  n = write(sc,record,lung);
  if(n == 0) 
    return -1;
  return n;

}

测试返回 receiveMessage 的 INVALID ARGUMENT 并且套接字中没有写入和读取消息，我认为问题出在缓冲区的长度(无符号整数)有什么建议吗？

Answer 1

查看联机帮助页以了解有关 EINVAL 的内容，您要么发送了无效的套接字，要么发送了无效的 read() 指针。尝试调试您的哪个 read() 调用也失败了。

但是这是错误的:

lung = read(sc, &(msg->buffer), sizeof(char)*msg->length);

你的缓冲区是一个指针，你想读取它指向的任何地方的数据，而不是它的地址。所以应该是

lung = read(sc, msg->buffer, sizeof(char)*msg->length);