Renci.SshNet.ForwardedPortDynamic.HandleSocks5 C# (CSharp) Method

        private bool HandleSocks5(Socket socket, IChannelDirectTcpip channel, TimeSpan timeout)
        {
            var authenticationMethodsCount = SocketAbstraction.ReadByte(socket, timeout);
            if (authenticationMethodsCount == -1)
            {
                // SOCKS client closed connection
                return false;
            }

            var authenticationMethods = new byte[authenticationMethodsCount];
            if (SocketAbstraction.Read(socket, authenticationMethods, 0, authenticationMethods.Length, timeout) == 0)
            {
                // SOCKS client closed connection
                return false;
            }

            if (authenticationMethods.Min() == 0)
            {
                // no user authentication is one of the authentication methods supported
                // by the SOCKS client
                SocketAbstraction.Send(socket, new byte[] { 0x05, 0x00 }, 0, 2);
            }
            else
            {
                // the SOCKS client requires authentication, which we currently do not support
                SocketAbstraction.Send(socket, new byte[] { 0x05, 0xFF }, 0, 2);

                // we continue business as usual but expect the client to close the connection
                // so one of the subsequent reads should return -1 signaling that the client
                // has effectively closed the connection
            }

            var version = SocketAbstraction.ReadByte(socket, timeout);
            if (version == -1)
            {
                // SOCKS client closed connection
                return false;
            }

            if (version != 5)
                throw new ProxyException("SOCKS5: Version 5 is expected.");

            var commandCode = SocketAbstraction.ReadByte(socket, timeout);
            if (commandCode == -1)
            {
                // SOCKS client closed connection
                return false;
            }

            var reserved = SocketAbstraction.ReadByte(socket, timeout);
            if (reserved == -1)
            {
                // SOCKS client closed connection
                return false;
            }

            if (reserved != 0)
            {
                throw new ProxyException("SOCKS5: 0 is expected for reserved byte.");
            }

            var addressType = SocketAbstraction.ReadByte(socket, timeout);
            if (addressType == -1)
            {
                // SOCKS client closed connection
                return false;
            }

            IPAddress ipAddress;
            byte[] addressBuffer;
            switch (addressType)
            {
                case 0x01:
                    {
                        addressBuffer = new byte[4];
                        if (SocketAbstraction.Read(socket, addressBuffer, 0, 4, timeout) == 0)
                        {
                            // SOCKS client closed connection
                            return false;
                        }

                        ipAddress = new IPAddress(addressBuffer);
                    }
                    break;
                case 0x03:
                    {
                        var length = SocketAbstraction.ReadByte(socket, timeout);
                        if (length == -1)
                        {
                            // SOCKS client closed connection
                            return false;
                        }
                        addressBuffer = new byte[length];
                        if (SocketAbstraction.Read(socket, addressBuffer, 0, addressBuffer.Length, timeout) == 0)
                        {
                            // SOCKS client closed connection
                            return false;
                        }

                        ipAddress = IPAddress.Parse(SshData.Ascii.GetString(addressBuffer, 0, addressBuffer.Length));

                        //var hostName = new Common.ASCIIEncoding().GetString(addressBuffer);

                        //ipAddress = Dns.GetHostEntry(hostName).AddressList[0];
                    }
                    break;
                case 0x04:
                    {
                        addressBuffer = new byte[16];
                        if (SocketAbstraction.Read(socket, addressBuffer, 0, 16, timeout) == 0)
                        {
                            // SOCKS client closed connection
                            return false;
                        }

                        ipAddress = new IPAddress(addressBuffer);
                    }
                    break;
                default:
                    throw new ProxyException(string.Format("SOCKS5: Address type '{0}' is not supported.", addressType));
            }

            var portBuffer = new byte[2];
            if (SocketAbstraction.Read(socket, portBuffer, 0, portBuffer.Length, timeout) == 0)
            {
                // SOCKS client closed connection
                return false;
            }

            var port = (uint)(portBuffer[0] * 256 + portBuffer[1]);
            var host = ipAddress.ToString();

            RaiseRequestReceived(host, port);

            channel.Open(host, port, this, socket);

            SocketAbstraction.SendByte(socket, 0x05);

            if (channel.IsOpen)
            {
                SocketAbstraction.SendByte(socket, 0x00);
            }
            else
            {
                SocketAbstraction.SendByte(socket, 0x01);
            }

            // reserved
            SocketAbstraction.SendByte(socket, 0x00);

            if (ipAddress.AddressFamily == AddressFamily.InterNetwork)
            {
                SocketAbstraction.SendByte(socket, 0x01);
            }
            else if (ipAddress.AddressFamily == AddressFamily.InterNetworkV6)
            {
                SocketAbstraction.SendByte(socket, 0x04);
            }
            else
            {
                throw new NotSupportedException("Not supported address family.");
            }

            var addressBytes = ipAddress.GetAddressBytes();
            SocketAbstraction.Send(socket, addressBytes, 0, addressBytes.Length);
            SocketAbstraction.Send(socket, portBuffer, 0, portBuffer.Length);

            return true;
        }