c# - 将图像从 C# 客户端发送到 C 服务器

Question

如果我发送纯文本就没有问题。一切都好。但是，如果我尝试从 C# 客户端发送图像，服务器会收到正确的字节数，但当我将缓冲区保存到文件(二进制模式 - wb)时，它总是有 4 个字节。

我通过 C# 客户端使用函数 File.ReadAllBytes() 发送它。

我的保存代码看起来像

   FILE * pFile;
   char *buf = ReceiveMessage(s);
   pFile = fopen (fileName , "wb");
   fwrite(buf, sizeof(buf[0]), sizeof(buf)/sizeof(buf[0]), pFile);
   fclose (pFile);
   free(buf);

我的接收函数是这样的

static unsigned char *ReceiveMessage(int s)
{
   int prefix;
   recv(s, &prefix, 4, 0);
   int len = prefix;
   char *buffer= (char*)malloc(len + 1);
   int received = 0, totalReceived = 0;
   buffer[len] = '\0';
   while (totalReceived < len)
   {
      if (len - totalReceived > BUFFER_SIZE)
      {
         received = recv(s, buffer + totalReceived, BUFFER_SIZE, 0);
      }
      else
      {
         received = recv(s, buffer + totalReceived, len - totalReceived, 0);
      }
      totalReceived += received;
   }

   return buffer;
}

Answer 1

您的 C 代码需要从 ReceiveMessage() 函数传回 len。

char *buf = ReceiveMessage(s);  // buf is a char*
... sizeof(buff)                // sizeof(char*) is 4 or 8

所以你需要类似的东西

 static unsigned char *ReceiveMessage(int s, int* lenOut)
 {
     ...
     *lenOut = totalReceived ;
 }