runtime: Socket.Select() method doesn't work correctly in linux.

I use linux mint mate 17.2 which is ubuntu and debian based. I cannot connect to Ngpsql database from Linux client. But I can connect from Windows client.

Because: After the following line is called =>Socket.Select(null, write, error, perIpTimeout);

In Linux: The list write doesn’t have any elements. As a result it enters the if (!write.Any()) block and creates “Timeout exception” there.

In Windows: The list write has the element. It works.

Here is a sample code to produce it. It is a console application that works on CoreClr.

// Program.cs
using System;
// using Npgsql;
using System.Net;
using System.Net.Sockets;
using System.Collections.Generic;
using System.Linq;

namespace Sample
{
    public class Program
    {
        public void Main()
        {
            Console.WriteLine("App started..");

            string Host = "192.168.1.72";
            int Port = 5432;

            int perIpTimeout = -1;
            var ips = Dns.GetHostAddressesAsync(Host).Result;
            var ep = new IPEndPoint(ips[0], Port);
            var socket = new Socket(ep.AddressFamily, SocketType.Stream, ProtocolType.Tcp)
            {
                Blocking = false
            };


            try
            {
                try
                {
                    socket.Connect(ep);
                }
                catch (SocketException e)
                {
                    if (e.SocketErrorCode != SocketError.WouldBlock)
                    {
                        throw;
                    }
                }
                var write = new List<Socket> { socket };
                var error = new List<Socket> { socket };
                Socket.Select(null, write, error, perIpTimeout);
                var errorCode = (int)socket.GetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Error);
                if (errorCode != 0)
                {
                    throw new SocketException((int)socket.GetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Error));
                }
                if (!write.Any())
                {
            // When it is Linux, it will enter this block here!
                    Console.WriteLine(
                        $"Timeout after {new TimeSpan(perIpTimeout * 10).TotalSeconds} seconds when connecting to {ips[0]}");
                    try { socket.Dispose(); }
                    catch
                    {
                        // ignored
                    }

                    // if i == 0
                    Console.WriteLine("i==0 exception");
                    throw new TimeoutException();

                    // continue;
                }
                socket.Blocking = true;

                return;
            }
            catch (TimeoutException) { throw; }
            catch
            {
                try { socket.Dispose(); }
                catch
                {
                    // ignored
                }

                Console.WriteLine("Failed to connect to " + ips[0]);

                // if (i == 0)

                Console.WriteLine("i==0 exception 2");
                throw;

            }
        }
    }

    // TODO: Remove. Will be fixed in the next release of EF.
    public class Startup
    {
        public void Configure() { }
    }
}