c - recvfrom() 错误 10035 使用非阻塞套接字

Question

我正在使用 ioctlsocket() 函数使我的套接字成为非阻塞的，但是当我调用 recvfrom() 时，我收到错误 10035 (WSAEWOULDBLOCK)。

u_long mode = 1;
ioctlsocket(newSocketIdentifier, FIONBIO, &mode);

while(1)
   {
      if((recv_len = recvfrom(newSocketIdentifier, receiveBuffer, sizeof(receiveBuffer), 0, (struct sockaddr *) &clientSocket, &clientSocketLength)) == SOCKET_ERROR)
      {
         char err[128];
         itoa(WSAGetLastError(),err,10);
         MessageBox( NULL,"Could not Receive Data",err,MB_ICONINFORMATION);
         BREAK;
      }
   }

谁能解释为什么会这样？ :(

Answer 1

如果没有可用数据，这是正常的。代码是 WSAEWOULDBLOCK(请参阅此表)，这意味着在阻塞端口上，函数必须等待直到它可以被服务。

   while(1)
   {
      if((recv_len = recvfrom(newSocketIdentifier, receiveBuffer, sizeof(receiveBuffer), 0, (struct sockaddr *) &clientSocket, &clientSocketLength)) == SOCKET_ERROR)
      { 
         int ierr= WSAGetLastError();
         if (ierr==WSAEWOULDBLOCK) {  // currently no data available
             Sleep(50);  // wait and try again
             continue; 
         }

         // Other errors
         char err[128];
         itoa(ierr,err,10);
         MessageBox( NULL,"Could not Receive Data",err,MB_ICONINFORMATION);
         break;
      }
   }