Tcpclient stream.Socket / stream关闭时，ReadAsync是否不返回0？

Question

I'm using TcpClient.Stream.ReadAsync to receive data in a loop. Traditionally, windows sockets return 0 when the socket closes gracefully. With the following code, the only time ReadAsync returns is when there is actual data. If I close the remote app (gracefully or forcefully) or even if I call Stream.Close() on the TcpClient, the ReadAsync still doesn't complete or throw an exception. How do I get ReadAsync to complete?

var amountRead = await stream.ReadAsync(conn.buffer, 0, Connection.BufferSize, ct);

if (amountRead == 0)
    break; //end of stream.
else
{
    //Process Received Data here
}

Answer 1

No, the ReadAsync reading semantics are exactly the same as BeginRead and Read . The read will return a 0-byte result at the end of the stream.

It's possible that the remote server is not closing the socket gracefully. Public-facing servers often do this to avoid the 4-way closing handshake. Unfortunately, this means that you as the client need to detect when the socket is closed. Traditionally, this is done by using a keepalive message or packet. I have a blog post with more details ; but the key is it has to be an active detection - ie, the client has to send something to detect the connection is no longer there.

On a side note, I'm not sure what closing the stream would do. But I'm fairly certain that closing the socket ( TcpClient ) would cause the stream read to complete with an error.