[Ethereum] Issue when I try a connection to geth using web3

Code

• geth version : v1.4.18-stable/linux/go1.5.1
• web3 version : 0.17.0-alpha

Here is the script I launch in a docker container to run geth :

#! /bin/bash
genesis_json_file=development/genesis_config/genesis_block.json
default_password=development/genesis_config/default_password # contain the password "toto"
datadir=data

rm -rf $datadir/*
geth --datadir $datadir init $genesis_json_file
geth --password $default_password --datadir $datadir account new
geth --datadir $datadir --mine --minerthreads 1 --rpc --rpcaddr "0.0.0.0" --rpcapi "eth,web3,personal"

Now, I am able to reach the geth API from my host system :

$ curl http://0.0.0.0:8545
> {"jsonrpc":"2.0","error":{"code":-32600,"message":"EOF"}}

Sometimes issues come when I try to connect to geth using web3. Here is my js script :

function connect(host, port) {
  uri = 'http://' + host + ':' + port;
  if (typeof web3 !== 'undefined') {
    web3 = new Web3(web3.currentProvider);
  }
  else {
    /* set the provider you want from Web3.providers */
    process.stdout.write('Setting Http provider : ' + uri + "\n")
    var prov = new Web3.providers.HttpProvider(uri);
    web3 = new Web3(prov);
  }

  if(!web3.isConnected()) {
    process.stdout.write('Cannot reach ' + uri + "\n");
    return false;
  }
  else {
    process.stdout.write('Connected to ' + uri + "\n");
    return true;
  }
}

function compile_contract(file_path) {
  # No problem here
  # This return the compiled contract
  ...
}

function send_contract_handler(e, contract) {
  if (e){
    console.log('send contract ERR : ' + e);
  }
  else if (typeof contract.address === 'undefined') {
    console.log("Contract transaction send. Hash: " + contract.transactionHash);
    console.log('Waiting for mining process');
  }
  else{
    console.log('Contract mined! address: ' + contract.address);
  }
}

function send_contract(from_addr, contract) {
  /* Unlock account */
  web3.eth.defaultAccount = from_addr;
  var ret = web3.personal.unlockAccount(from_addr, 'toto');
  /* Get account balance */
  var balance = web3.eth.getBalance(from_addr);
  /* Ask for a gas price estimation to send the contract */
  var estimation = web3.eth.estimateGas({
    from: from_addr,
    data: contract.bytecode
  });
  /* Check if the sender account has enough gas */
  if (estimation > parseInt(balance.toString(10)))
    console.log('estimation to high : not enought gas');

  /* Send the contract creation transaction to the block chain */
  return web3.eth.contract(JSON.parse(contract.interface)).new(
    {
      from: from_addr,
      data: contract.bytecode,
      gas: estimation
    },
    send_contract_handler
  );
}

if (require.main === module) {
  /* Connect to a running node */
  while (!connect('0.0.0.0', 8545));

  /* Compile contract */
  var output = compile_contract(contractPath);
  if (!output)
    return 2;

  /* Send contract using the coinbase addr */
  return send_contract(web3.eth.coinbase, output);
}

Issues

When I run this script I have 3 different possible scenarios for the same code:

1. All works perfectly fine. Script output:

   Setting Http provider : http://0.0.0.0:8545
   Connected to http://0.0.0.0:8545
   ./contract/simple.sol will be compiled
   from_addr : 0x5b481d0f036af15ec3025fed428cdd49b45b4a3e
   Contract transaction send. Hash: 0x95cf8c756860605cefd5ef89fe673fa3a267dfb66766cf4a0d38b94194053935
   Waiting for mining process
   Contract mined! address: 0x4af7d1639f590dfc9e5594a3ba0bb9ead17a14bc
   

2. I am not able to be connected to the node: web3.isConnected() always return false. Script output:

   Cannot reach http://0.0.0.0:8545
   Cannot reach http://0.0.0.0:8545
   ...
   Cannot reach http://0.0.0.0:8545
   

3. The connection failed on this line :

    var balance = web3.eth.getBalance(from_addr);
   

   Script output:

   Setting Http provider : http://0.0.0.0:8545
   Connected to http://0.0.0.0:8545
   ./contract/simple.sol will be compiled
   from_addr : 0x5b481d0f036af15ec3025fed428cdd49b45b4a3e
   /home/xxx/node_modules/solc/soljson.js:1
   (function (exports, require, module, __filename, __dirname) { var     Module;if(!Module)Module=(typeof Module!=="undefined"?Module:null)||{};var moduleOverrides={};for(var key in Module){if(Module.hasOwnProperty(key)){moduleOverrides[key]=Module[key]}}var ENVIRONMENT_IS_WEB=typeof window==="object";var ENVIRONMENT_IS_WORKER=typeof importScripts==="function";var ENVIRONMENT_IS_NODE=typeof process==="object"&&typeof require==="function"&&!ENVIRONMENT_IS_WEB&&!ENVIRONMENT_IS_WORKER;var ENVIRONMENT_IS_SHELL=!ENVIRONMENT_IS_WEB&&!ENVIRONMENT_IS_NODE&&!ENVIRONMENT_IS_WORKER;if(ENVIRONMENT_IS_NODE){if(!Module["print"])Module["print"]=function print(x){process["stdout"].write(x+"\n")};if(!Module["printErr"])Module["printErr"]=function printErr(x){process["stderr"].write(x+"\n")};var nodeFS=require("fs");var nodePath=require("path");Module["read"]=function read(filename,binary){filename=nodePath["normalize"](filename);var ret=nodeFS["readFileSync"](fi
   
   Error: CONNECTION ERROR: Couldn't connect to node http://0.0.0.0:8545.
   at Object.InvalidConnection (/home/xxx/node_modules/web3/lib/web3/errors.js:28:16)
   at HttpProvider.send (/home/xxx/node_modules/web3/lib/web3/httpprovider.js:75:22)
   at RequestManager.send (/home/xxx/node_modules/web3/lib/web3/requestmanager.js:58:32)
   at Eth.send [as getBalance] (/home/xxx/node_modules/web3/lib/web3/method.js:145:58)
   at send_contract (/home/xxx/myscript.js:76:26)
   at Object.<anonymous> (/home/xxx/myscript.js:108:10)
   at Module._compile (module.js:556:32)
   at Object.Module._extensions..js (module.js:565:10)
   at Module.load (module.js:473:32)
   at tryModuleLoad (module.js:432:12)
   

Hints

• Scenario 1 is the most common scenario. This usually happen when I just restart my computer
• Scenario 2 – 3 usually appears after some successful try
• Even in scenario 2 – 3 I am able to reach the get API with curl or telnet

This seems to be a network issue or a bad state in geth…

Sorry for this long and imprecise question.
If someone have an idea why this happen, or a good method to debug it, he will be welcome!