recv读取不完整的数据包

Question

I have simple function that responsible on receiving packets via socket.

if((recv_size = recv(sock , rx , 50000 ,0)) == SOCKET_ERROR)
  {
    ...                         
  } else
  {
    ...
  }

I found that sometimes I receiv incompleate packet. Why? Mybe I should use recv for several times? Packet length never exceeds 50000 bytes.

I use TCP socket.

Answer 1

If you're using TCP it's expected. TCP is a streaming protocol, it doesn't have "packets" or message boundaries, and you can have received all of the "message" or part of it, or even multiple messages. So you might have to call recv multiple times to receive a complete message.

However, since TCP doesn't have message boundaries, you have to implement them yourself on top of TCP, for example by sending the length of the message in a fixed-size header, or have some special end-of-message marker.