Bitcoin

We can check the transaction and balance at explore website such as BlockCypher.

I want to make Android Bitcoin wallet without SPV node. I have to fetch balance, transactions and send BTC by JSON-RPC API with someone's full node. The other solution is using third-party API such as blockchain.com, BlockCypher and Coinbase.

Get balance

One possible solution is use JSON-RPC API to get all transactions, then keep the relative transactions with user address. Finally calculating its UXTO to get the final balance. But using third-party API to get the balance is easier.

• blockchain.com

  Get https://blockchain.info/rawaddr/$address
  
  // response
  {
      "hash160":"660d4ef3a743e3e696ad990364e555c271ad504b",
      "address":"1AJbsFZ64EpEfS5UAjAfcUG8pH8Jn3rn1F",
      "n_tx":17,
      "n_unredeemed":2,
      "total_received":1031350000,
      "total_sent":931250000,
      "final_balance":100100000,
      "txs":[--Array of Transactions--]
  }
  

Get transactions

The gettransaction JSON-RPC API can get the transaction only for the wallet in host node. So we have to use getrawtransaction API. And second parameter should be true so that we can get the JSON response.

{
    "jsonrpc":"2.0",
    "method":"getrawtransaction",
    "params":["301e88f1bf7d261c63d063e3a1707a505ca6dcb9014f12247bb461188d20614c", true], // Testnet
    "id": 1
}

{
    "result": {
        "txid": "301e88f1bf7d261c63d063e3a1707a505ca6dcb9014f12247bb461188d20614c",
        "hash": "4def7a882946d7c9cc09aae49517fe8fe71ac6d7b231f65d225193a7e33d458a",
        "version": 2,
        "size": 245,
        "vsize": 164,
        "weight": 653,
        "locktime": 1541608,
        "vin": [
            {
                "txid": "7a5b07fcfccc0aa546db265638102ad11a5558dbf1008c6de2877079f1b2713b",
                "vout": 36,
                "scriptSig": {
                    "asm": "0014e03fc8188a85321a909eb8f5d3ed5f53573e0594",
                    "hex": "160014e03fc8188a85321a909eb8f5d3ed5f53573e0594"
                },
                "txinwitness": [
                    "304402200478d8e61405a250a84b5717a1c330fc270a8ce69056032b897b84788ce462cb02205df2b6425083d046e4f8f8df5f93795045f7818425235588575293c79f07b7d901",
                    "027f712362142b9709ef29caff6f520dbf600e041bb94ccc23e1941164f313667f"
                ],
                "sequence": 4294967294
            }
        ],
        "vout": [
            {
                "value": 0.01,
                "n": 0,
                "scriptPubKey": {
                    "asm": "0 682b103184441f62bc82b60478196bb862ca1d70",
                    "hex": "0014682b103184441f62bc82b60478196bb862ca1d70",
                    "reqSigs": 1,
                    "type": "witness_v0_keyhash",
                    "addresses": [
                        "tb1qdq43qvvygs0k90yzkcz8sxtthp3v58ts599yfv"
                    ]
                }
            },
            {
                "value": 0.01099672,
                "n": 1,
                "scriptPubKey": {
                    "asm": "0 44525400c97bd32550ccc68952db4321d1b2799d",
                    "hex": "001444525400c97bd32550ccc68952db4321d1b2799d",
                    "reqSigs": 1,
                    "type": "witness_v0_keyhash",
                    "addresses": [
                        "tb1qg3f9gqxf00fj25xvc6y49k6ry8gmy7vatznqs0"
                    ]
                }
            }
        ],
        "hex": "020000000001013b71b2f1797087e26d8c00f1db58551ad12a10385626db46a50accfcfc075b7a2400000017160014e03fc8188a85321a909eb8f5d3ed5f53573e0594feffffff0240420f0000000000160014682b103184441f62bc82b60478196bb862ca1d7098c710000000000016001444525400c97bd32550ccc68952db4321d1b2799d0247304402200478d8e61405a250a84b5717a1c330fc270a8ce69056032b897b84788ce462cb02205df2b6425083d046e4f8f8df5f93795045f7818425235588575293c79f07b7d90121027f712362142b9709ef29caff6f520dbf600e041bb94ccc23e1941164f313667fe8851700",
        "blockhash": "000000000000015bec9f6aa9e2cdc6e402f1657804f718710b553bf059fb298d",
        "confirmations": 661,
        "time": 1560155793,
        "blocktime": 1560155793
    },
    "error": null,
    "id": 1
}

Send transaction

We can use sendrawtransaction JSON-RPC API to send BTC. But first we have to create transaction and sign it.

Address myTBdQRS6h5DFSQ8o5nR7wgUwoqgRj2U7t received BTC from faucet in transaction b4e09a90d5e0054b2e08ba8d6f7e2a80962baef528d1b91353639aa778a80610 .

• from address myTBdQRS6h5DFSQ8o5nR7wgUwoqgRj2U7t has 0.07508694 BTC
• to address n1wMf2JJxFNdQ6DWaaMzPg5ZZXwA6UkRTv has no balance

First step is call createrawtransaction .

{
    "jsonrpc":"2.0",
    "method":"createrawtransaction",
    "params":[
            [{
                "txid":"b4e09a90d5e0054b2e08ba8d6f7e2a80962baef528d1b91353639aa778a80610",
                "vout": 1
            }], 
            [{
                "n1wMf2JJxFNdQ6DWaaMzPg5ZZXwA6UkRTv": 0.00123
            }]
        ],
    "id": 1
}

{
    "result": "02000000011006a878a79a635313b9d128f5ae2b96802a7e6f8dba082e4b05e0d5909ae0b40100000000ffffffff0178e00100000000001976a914dfffffff373af20b31bf975abe3e2ae55fefa69488ac00000000",
    "error": null,
    "id": 1
}

Then call signrawtransactionwithkey with our private key.

{
    "jsonrpc":"2.0",
    "method":"signrawtransactionwithkey",
    "params":[
            "02000000011006a878a79a635313b9d128f5ae2b96802a7e6f8dba082e4b05e0d5909ae0b40100000000ffffffff0178e00100000000001976a914dfffffff373af20b31bf975abe3e2ae55fefa69488ac00000000",
            ["936L4d7HsoXVRpbPrYXZP4YbuwxqDoBt6anRnNeUvcvPaP2DLEm"]
        ],
    "id": 1
}

{
    "result": {
        "hex": "02000000011006a878a79a635313b9d128f5ae2b96802a7e6f8dba082e4b05e0d5909ae0b4010000008a47304402203a247421f93aa99bb2e82777cab859d55c6d68ed163a0b2228843f4655df9bd202203afa00dc76fdc824a85a43b9c3833164b587fa1072595855230800dcaf681b4e014104a0ad9f0f9b0ae8bd9bae13e81cae8fda00bbc791f29f0f8daa8cffb4aaaeb3e1595d2c938f77af1e0db4e6db25880c66c73f5d55d3ed59032e574d6bedfcb07affffffff0178e00100000000001976a914dfffffff373af20b31bf975abe3e2ae55fefa69488ac00000000",
        "complete": true
    },
    "error": null,
    "id": 1
}

Finally, call sendrawtransaction .

{
    "jsonrpc":"2.0",
    "method":"sendrawtransaction",
    "params":["02000000011006a878a79a635313b9d128f5ae2b96802a7e6f8dba082e4b05e0d5909ae0b4010000008a47304402203a247421f93aa99bb2e82777cab859d55c6d68ed163a0b2228843f4655df9bd202203afa00dc76fdc824a85a43b9c3833164b587fa1072595855230800dcaf681b4e014104a0ad9f0f9b0ae8bd9bae13e81cae8fda00bbc791f29f0f8daa8cffb4aaaeb3e1595d2c938f77af1e0db4e6db25880c66c73f5d55d3ed59032e574d6bedfcb07affffffff0178e00100000000001976a914dfffffff373af20b31bf975abe3e2ae55fefa69488ac00000000"],
    "id": 1
}

{
    "result": "c544bf3b622c3d8e6e967c2d6e103bb26ba86d850001ae2bfa0f924210c6e94b",
    "error": null,
    "id": 1
}

Now, address n1wMf2JJxFNdQ6DWaaMzPg5ZZXwA6UkRTv has 0.00123 BTC.

Input not found or already spent error

When I call createrawtransaction with zero vout, I got error of sendrawtransaction .

{
    "jsonrpc":"2.0",
    "method":"createrawtransaction",
    "params":[
            [{
                "txid":"b4e09a90d5e0054b2e08ba8d6f7e2a80962baef528d1b91353639aa778a80610",
                "vout": 0
            }], 
            [{
                "n1wMf2JJxFNdQ6DWaaMzPg5ZZXwA6UkRTv":"0.00123"
            }]
        ],
    "id": 1
}

{
    "jsonrpc":"2.0",
    "method":"signrawtransactionwithkey",
    "params":[
            "02000000011006a878a79a635313b9d128f5ae2b96802a7e6f8dba082e4b05e0d5909ae0b40000000000ffffffff0178e00100000000001976a914dfffffff373af20b31bf975abe3e2ae55fefa69488ac00000000",
            ["936L4d7HsoXVRpbPrYXZP4YbuwxqDoBt6anRnNeUvcvPaP2DLEm"]
        ],
    "id": 1
}

{
    "result": {
        "hex": "02000000011006a878a79a635313b9d128f5ae2b96802a7e6f8dba082e4b05e0d5909ae0b40000000000ffffffff0178e00100000000001976a914dfffffff373af20b31bf975abe3e2ae55fefa69488ac00000000",
        "complete": false,
        "errors": [
            {
                "txid": "b4e09a90d5e0054b2e08ba8d6f7e2a80962baef528d1b91353639aa778a80610",
                "vout": 0,
                "witness": [],
                "scriptSig": "",
                "sequence": 4294967295,
                "error": "Input not found or already spent"
            }
        ]
    },
    "error": null,
    "id": 1
}

I change vout to be 1 to fix it.

BlockCypher

Bitcoin Testnet Explore

blockchain.com API

Bitcoin Core API