class Net::SSH::Proxy::SOCKS5

def open(host, port, connection_options)
  socket = Socket.tcp(proxy_host, proxy_port, nil, nil,
                      connect_timeout: connection_options[:timeout])
  methods = [METHOD_NO_AUTH]
  methods << METHOD_PASSWD if options[:user]
  packet = [VERSION, methods.size, *methods].pack("C*")
  socket.send packet, 0
  version, method = socket.recv(2).unpack("CC")
  if version != VERSION
    socket.close
    raise Net::SSH::Proxy::Error, "invalid SOCKS version (#{version})"
  end
  if method == METHOD_NONE
    socket.close
    raise Net::SSH::Proxy::Error, "no supported authorization methods"
  end
  negotiate_password(socket) if method == METHOD_PASSWD
  packet = [VERSION, CMD_CONNECT, 0].pack("C*")
  if host =~ /^(\d+)\.(\d+)\.(\d+)\.(\d+)$/
    packet << [ATYP_IPV4, $1.to_i, $2.to_i, $3.to_i, $4.to_i].pack("C*")
  else
    packet << [ATYP_DOMAIN, host.length, host].pack("CCA*")
  end
  packet << [port].pack("n")
  socket.send packet, 0
  
  version, reply, = socket.recv(2).unpack("C*")
  socket.recv(1)
  address_type = socket.recv(1).getbyte(0)
  case address_type
  when 1
    socket.recv(4)  # get four bytes for IPv4 address
  when 3
    len = socket.recv(1).getbyte(0)
    hostname = socket.recv(len)
  when 4
    ipv6addr hostname = socket.recv(16)
  else
    socket.close
    raise ConnectError, "Illegal response type"
  end
  portnum = socket.recv(2)
  
  unless reply == SUCCESS
    socket.close
    raise ConnectError, "#{reply}"
  end
  return socket
end