如何区分套接字中的读取错误和写入错误？

Question

I am creating a server for a game that deals with lots of TCP connections, and I need to deal with a sudden loss of connection (pc crash, game process killed, internet connection lost, ectect). The problem I currently have is that I can't tell apart a read error from a write error since both throw an IOException . even the underlying exception is the same ( SocketException ), the only difference being that one occurs on Socket.Send() and the other on Socket.Receive() respectively. I could of course compare the exception message, but that would become a problem as soon as the system language changes (and lets be honest, that would be a pretty messy approach anyway).

I tried comparing the Hresult but since the underlying exception is the same, so is the Hresult . I also tried getHashCode() but this one changes from player to player.

Any other ways I could tell apart those 2 situations? To clarify, we're talking about the exception that comes up when using TcpClient.read() or TcpClient.write() on a TcpClient whose connection has been unexpectedly closed.

Answer 1

You could try wrapping the send and receive functions in a try-catch block, and use the Data property to tell exceptions from read and write apart:

enum ReadOrWrite { Read, Write }

void Foo()
{
    try
    {
        socket.Receive();
    }
    catch (IOException ex)
    {
        ex.Data.Add("readOrWrite", ReadOrWrite.Read);
        throw;
    }
}

And this is where you later catch it:

try
{
    Foo();
}
catch (IOException ex) when (ex.Data.Contains("readOrWrite"))
{
    var readOrWrite = ex.Data["readOrWrite"];
}