php与ethereum rpc server通信

一、Json RPC

Json RPC就是基于json的远程过程调用,这么解释比较抽象。简单来说,就是post一个json格式的数据调用rpc server中的方法. 而这个json格式是固定的, 总的来说有这么几项:

{ "method": "", "params": [], "id": idNumber }

method: 方法名

params: 参数列表

id: 对过程调用的唯一标识号

二、构建一个Json RPC客户端

<?php class jsonRPCClient { /** * Debug state * * @var boolean */ private $debug; /** * The server URL * * @var string */ private $url; /** * The request id * * @var integer */ private $id; /** * If true, notifications are performed instead of requests * * @var boolean */ private $notification = false; /** * Takes the connection parameters * * @param string $url * @param boolean $debug */ public function __construct($url,$debug = false) { // server URL $this->url = $url; // proxy empty($proxy) ? $this->proxy = '' : $this->proxy = $proxy; // debug state empty($debug) ? $this->debug = false : $this->debug = true; // message id $this->id = 1; } /** * Sets the notification state of the object. In this state, notifications are performed, instead of requests. * * @param boolean $notification */ public function setRPCNotification($notification) { empty($notification) ? $this->notification = false : $this->notification = true; } /** * Performs a jsonRCP request and gets the results as an array * * @param string $method * @param array $params * @return array */ public function __call($method,$params) { // check if (!is_scalar($method)) { throw new Exception('Method name has no scalar value'); } // check if (is_array($params)) { // no keys $params = $params[0]; } else { throw new Exception('Params must be given as array'); } // sets notification or request task if ($this->notification) { $currentId = NULL; } else { $currentId = $this->id; } // prepares the request $request = array( 'method' => $method, 'params' => $params, 'id' => $currentId ); $request = json_encode($request); $this->debug && $this->debug.='***** Request *****'."\n".$request."\n".'***** End Of request *****'."\n\n"; // performs the HTTP POST $opts = array ('http' => array ( 'method' => 'POST', 'header' => 'Content-type: application/json', 'content' => $request )); $context = stream_context_create($opts); if ($fp = fopen($this->url, 'r', false, $context)) { $response = ''; while($row = fgets($fp)) { $response.= trim($row)."\n"; } $this->debug && $this->debug.='***** Server response *****'."\n".$response.'***** End of server response *****'."\n"; $response = json_decode($response,true); } else { throw new Exception('Unable to connect to '.$this->url); } // debug output if ($this->debug) { echo nl2br($debug); } // final checks and return if (!$this->notification) { // check if ($response['id'] != $currentId) { throw new Exception('Incorrect response id (request id: '.$currentId.', response id: '.$response['id'].')'); } if (!is_null($response['error'])) { throw new Exception('Request error: '. var_export($response['error'], true)); } return $response['result']; } else { return true; } } } ?>

比较简单的代码,如果比较懒,拿过去用就行了。也可以上packagist.org自己找一个rpc client.

三、调用RPC的两类方法

有两类方法需要调用. 一类是RPC server自带方法,另一类就是合约方法.

RPC server方法调用json格式

{ "method": "eth_accounts", "params": [], "id": 1 }

RPC Server自带方法的列表

调用自带方法比较简单,参考上述链接,大部分都有示例.

合约方法调用json格式

调用合约方法必须使用自带方法中的eth_call. 而合约方法名称和合约方法参数列表则使用params进行体现, 比如: 我们要调用合约中的balanceOf方法, 则json数据应该如何构造呢?

首先看看getBalanace的函数实现:

function balanceOf(address _owner) public view returns (uint256 balance)

提炼出函数原型:

balanceOf(address)

在geth控制台下运行命令:

web3.sha3("balanceOf(address)").substring(0, 10)

得到函数hash "0x70a08231"

假设待查询的地址 address _owner = "0x38aabef4cd283ccd5091298dedc88d27c5ec5750", 则去掉前面的"0x", 并在左边补24个零(一般地址长度为42位, 去掉'0x'后为40位),构成64位十六进制参数.

最终得到的参数为 "0x70a0823100000000000000000000000038aabef4cd283ccd5091298dedc88d27c5ec5750"

假设我们的合约地址为 "0xaeab4084194B2a425096fb583Fbcd67385210ac3".

则得到最终的json数据为:

{ "method": "eth_call", "params": [{"from": "0x38aabef4cd283ccd5091298dedc88d27c5ec5750", "to": "0xaeab4084194B2a425096fb583Fbcd67385210ac3", "data": "0x70a0823100000000000000000000000038aabef4cd283ccd5091298dedc88d27c5ec5750"}, "latest"], "id": 1 }

把以上json数据以post方式发送给服务器,就可以调用合约方法"balanceOf", 查询给定的地址中的代币余额.

调用合约中的其他方法也要新遵循上面的方式, 我们再分析一下transfer方法, 加深印象:

首先, 看看代码中的函数实现:

function transfer(address _to, uint256 _value) public returns (bool)

其次, 提炼出函数原型:

transfer(address,uint256) //注意逗号后面不能有空格

再次, 在控制台运行sha3函数:

web3.sha3("transfer(address,uint256)").substring(0, 10)

得到函数hash "0xa9059cbb"

第一个参数假设 address _to = "0x38aabef4cd283ccd5091298dedc88d27c5ec5750", 则去"0x", 补零到64位.

第二个参数假设 uint256 _value = 43776, 则化为十六进制"0xab00"后, 去"0x", 补零到64位.

连接起来

"0xa9059cbb00000000000000000000000038aabef4cd283ccd5091298dedc88d27c5ec5750000000000000000000000000000000000000000000000000000000000000ab00"