Respuesta JSON RPC no válida: "400 Bad Request" en Simple Embark Dapp

soy nuevo en Embark, siguiendo mi primer tutorial aquí en https://hackernoon.com/how-to-create-a-token-factory-with-ethereum-part-1-85e84d1f38fc

Cuando ejecuto lo siguiente en la consola

Token._supply().toNumber()

me sale el error

Respuesta JSON RPC no válida: "400 Solicitud incorrecta".

¿Qué hice mal?

Hasta ahora, esto es lo que hice

1. embark new TokenFactory&&cd TokenFactory
2. embark blockchain
3. embark run
4. Contrato de solidez añadido aapp/contracts/token.sol

Luego, en la consola de embarque, ejecuté el comando Token._supply().toNumber().

ficha.sol

pragma solidity ^0.4.8;
contract Token {

  event Transfer(address indexed from, address indexed to, uint value);
  event Approval( address indexed owner, address indexed spender, uint value);

  mapping( address => uint ) _balances;
  mapping( address => mapping( address => uint ) ) _approvals;
  uint public _supply;
  function Token( uint initial_balance ) {
    _balances[msg.sender] = initial_balance;
    _supply = initial_balance;
  }
  function totalSupply() constant returns (uint supply) {
    return _supply;
  }
  function balanceOf( address who ) constant returns (uint value) {
    return _balances[who];
  }
  function transfer( address to, uint value) returns (bool ok) {
    if( _balances[msg.sender] < value ) {
      throw;
    }
    if( !safeToAdd(_balances[to], value) ) {
      throw;
    }
    _balances[msg.sender] -= value;
    _balances[to] += value;
    Transfer( msg.sender, to, value );
    return true;
  }
  function transferFrom( address from, address to, uint value) returns (bool ok) {
    // if you don't have enough balance, throw
    if( _balances[from] < value ) {
      throw;
    }
    // if you don't have approval, throw
    if( _approvals[from][msg.sender] < value ) {
      throw;
    }
    if( !safeToAdd(_balances[to], value) ) {
      throw;
    }
    // transfer and return true
    _approvals[from][msg.sender] -= value;
    _balances[from] -= value;
    _balances[to] += value;
    Transfer( from, to, value );
    return true;
  }
  function approve(address spender, uint value) returns (bool ok) {
    // TODO: should increase instead
    _approvals[msg.sender][spender] = value;
    Approval( msg.sender, spender, value );
    return true;
  }
  function allowance(address owner, address spender) constant returns (uint _allowance) {
    return _approvals[owner][spender];
  }
  function safeToAdd(uint a, uint b) internal returns (bool) {
    return (a + b >= a);
  }
}

Registros

========================
Welcome to Embark 2.6.0
========================
Building Assets
loading solc compiler..
compiling contracts...
token.sol:10:3: Warning: No visibility specified. Defaulting to "public".
  function Token( uint initial_balance ) {
  ^
Spanning multiple lines.

token.sol:14:3: Warning: No visibility specified. Defaulting to "public".
  function totalSupply() constant returns (uint supply) {
  ^
Spanning multiple lines.

token.sol:17:3: Warning: No visibility specified. Defaulting to "public".
  function balanceOf( address who ) constant returns (uint value) {
  ^
Spanning multiple lines.

token.sol:20:3: Warning: No visibility specified. Defaulting to "public".
  function transfer( address to, uint value) returns (bool ok) {
  ^
Spanning multiple lines.

token.sol:22:7: Warning: "throw" is deprecated in favour of "revert()", "require()" and "assert()".
      throw;
      ^---^

token.sol:25:7: Warning: "throw" is deprecated in favour of "revert()", "require()" and "assert()".
      throw;
      ^---^

token.sol:32:3: Warning: No visibility specified. Defaulting to "public".
  function transferFrom( address from, address to, uint value) returns (bool ok) {
  ^
Spanning multiple lines.

token.sol:35:7: Warning: "throw" is deprecated in favour of "revert()", "require()" and "assert()".
      throw;
      ^---^

token.sol:39:7: Warning: "throw" is deprecated in favour of "revert()", "require()" and "assert()".
      throw;
      ^---^

token.sol:42:7: Warning: "throw" is deprecated in favour of "revert()", "require()" and "assert()".
      throw;
      ^---^

token.sol:51:3: Warning: No visibility specified. Defaulting to "public".
  function approve(address spender, uint value) returns (bool ok) {
  ^
Spanning multiple lines.

token.sol:57:3: Warning: No visibility specified. Defaulting to "public".
  function allowance(address owner, address spender) constant returns (uint _allowance) {
  ^
Spanning multiple lines.

token.sol:60:3: Warning: Function state mutability can be restricted to pure
  function safeToAdd(uint a, uint b) internal returns (bool) {
  ^
Spanning multiple lines.

deploying contracts
Token already deployed at 0x4dbe9239321ddf4eae6eb32f83c1a50d3c426510
finished deploying contracts
writing file dist/css/app.css
writing file dist/js/app.js
writing file dist/index.html
Watching for changes
ready to watch file changes