title: Send transactions to Ethereum contracts via JSON RPC API
body: <p>I'm playing around with <code>geth</code> and wanted to interacts with contracts through JSON RPC API. However, I'm confused because there is no place for <code>input</code> in the <code>eth.sendTransaction</code> API.</p>
  
  <p>Per <a href="https://ethereum.gitbooks.io/frontier-guide/content/rpc.html#eth_sendtransaction" rel="nofollow">Ethereum Gitbook</a>, <code>eth.sendTransaction</code> takes in params like this:</p>
  
  <pre><code>params: [{
    "from": "0xb60e8dd61c5d32be8058bb8eb970870f07233155",
    "to": "0xd46e8dd67c5d32be8058bb8eb970870f072445675",
    "gas": "0x76c0", // 30400,
    "gasPrice": "0x9184e72a000", // 10000000000000
    "value": "0x9184e72a", // 2441406250
    "data": "0xd46e8dd67c5d32be8d46e8dd67c5d32be8058bb8eb970870f072445675058bb8eb970870f072445675"
  }]
  </code></pre>
  
  <p>All these fields make sense but there is no place to specify the input. Using other tools, such as console and web apps, I can <code>sendTransaction</code> and noticed the TX takes a form like this:</p>
  
  <pre><code>&gt; eth.getTransactionFromBlock(60)
  {
    blockHash: "0xc386191621e45e170d50c1caacc9090b7117e09d0847c46f77f6a3c822ec5580",
    blockNumber: 60,
    from: "0xd9b56ae6e0f7a7e0e0dec74b685b2c7f3f543472",
    gas: 66666,
    gasPrice: 50000000000,
    hash: "0x28aa9e720e11f2f81490b6500a3a56c19ec77b936fc745d16c302387837f324e",
    input: "0xc6888fa10000000000000000000000000000000000000000000000000000000000000064",
    nonce: 6,
    to: "0x689495d3e1ff1b955bc4d0bde622bdb34dbb787b",
    transactionIndex: 0,
    value: 0
  }
  </code></pre>
  
  <p>Note the there is an <strong>input</strong> field. So is it possible to send transaction via JSON RPC API? If so, which API should be used?</p>