[Mono-list] Listen on same port ipv4 and ipv6

[J Decker]

On Fri, Dec 11, 2015 at 2:33 PM, J Decker <d3ck0r at gmail.com> wrote:
> On Fri, Dec 11, 2015 at 1:56 PM, J Decker <d3ck0r at gmail.com> wrote:
>> On Fri, Dec 11, 2015 at 1:50 PM, J Decker <d3ck0r at gmail.com> wrote:
>>> (First let me vent a little and say I LOVE all the consistency in
>>> network libraries; in MS.NET closing a IPV6 TcpClient sets Client to
>>> null, whereas IPV4 TcpCLient only disposes the object)
>>>
>>> I found this old message with no responses..
>>>
>>> http://lists.ximian.com/pipermail/mono-list/2014-May/050905.html
>>>
>>> I want to listen at the same port address at 0.0.0.0 and :: (ipv4 and
>>> 6 address respectively)
>>>
>>> in C I would open two listeners.  But I think maybe the .NET runtime
>>> is pre-checking if that port is already used in some internal list of
>>> sockets before attemping to open it in reality.
>>>
>>> in C# I will have to do the same thing, since connecting to the v6
>>> address with only the v4 listener at 0.0.0.0 listening fails to
>>> connect and times out.
>>>
>>> On Windows I have to, and it works; but again with Mono on Linux it
>>> doesn't work.
>>
>> This is the code that fails.
>>
>> internal GameServer()
>> {
>> byte[] raw_ipv4 = { 0, 0, 0, 0 };
>> IPAddress addr = new IPAddress( raw_ipv4 );
>> listener = new TcpListener( addr, Settings.Read( "Server Port",
>> GameServer.serving_port ) );
>> listener.Start();
>> byte[] raw_ipv6 = { 0,0,0,0
>> ,0, 0, 0, 0
>> ,0, 0, 0, 0
>> ,0, 0, 0, 0 };
>> IPAddress addr_v6 = new IPAddress( raw_ipv6 );
>> listener_v6 = new TcpListener( addr_v6, Settings.Read( "Server Port",
>> GameServer.serving_port ) );
>> listener_v6.Start(); /* Exception - EADDRINUSE ; even though it's not
>> and needs to be opened */
>> }

Supposedly this is the fix.  (I checked my C code and remembered I was
doing something with SetSockOpt)
_Socket.SetSocketOption(SocketOptionLevel.Socket,
SocketOptionName.ReuseAddress, True)

But GetSocketOption returns 1 for reuse to start with... and setting
it doesn't seem to do anything :(