Bug in Mono System.Net.Socket or I misunderstand something? (incorrect number of bytes sent returned)

After playing a while with Mono, I see one strange thing - every call to Send(), EndSend(), SendAsync() etc return not number of bytes sent in this particular operation, but total number of bytes sent during the lifetime of a Socket.

According to various sources (including official Microsoft documentation), the number of bytes sent should reflect only last operation (which seems logical and standard), b开发者_如何转开发ut in Mono this is different.

I've tried Mono 2.8.2, 2.10.5 - this behaviour is still there. Looking into sources (including master on GitHub), I see that this is "behaviour by design", however, this contradicts to documented behaviour.

So, my question is - is this a bug in Mono, or I misunderstood something? If this is a bug - how could it happen that it lurks there for years, and nobody noticed?

Sorry, but can't reproduce that with Send or EndSend. Considering test program and Mono's source code I would say there is no bug in Mono. Details below.

I used this code to test, it is not beautiful, however shows what should be shown:

using System;
using System.Net.Sockets;
using System.Net;
using System.Threading;

namespace Test2
{
    class MainClass
    {
        public static void Main (string[] args)
        {       
            var t = new Thread(Read) { IsBackground = true };
            t.Start();
            Thread.Sleep(300);
            var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            socket.Connect(new IPEndPoint(IPAddress.Loopback, 1234));
            for(var i = 0; i < 10; i++)
            {
                Console.WriteLine(socket.Send(new [] {(byte) 0x12}));
            }
        }

        public static void Read()
        {
            var s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            s.Bind(new IPEndPoint(IPAddress.Loopback, 1234));
            s.Listen(1);
            var accepted = s.Accept();
            while(true)
            {
                accepted.Receive(new byte[1]);
            }
        }
    }
}

On my machine output is:

1
1
1
1
1
1
1
1
1
1

Which is what expected. I was testing using Mono from git commit b21a860 on Ubuntu 10.10. About send_so_far, you mentioned: please notice, that call to int Send (byte [] buf) calls internal int Send_nochecks(...) and this in turn calls int Send_internal (socket, buf, offset, size, flags, out nativeError) which is tagged with [MethodImplAttribute (MethodImplOptions.InternalCall)] (so implemented directly in runtime) and uses no send_so_far at all. (As far as I can see, send_so_far is used in AsyncResult, but only in one AsyncResult, therefore it does not have to be zeroed - you can't call EndSend twice on same AsyncResult.).

EDIT:

I have just tested it with async version (i.e. EndSend) and it works properly too. Could you post some piece of problematic code?