Ethereum: Using JSON-RPC in C++ on Linux
In this article, we will guide you through the process of using the JSON-RPC protocol in C++ to interact with the Ethereum blockchain. We will also cover how to use RPC libraries for Bitcoin and provide examples of using Electrum API.
What is JSON-RPC?
JSON-RPC (JavaScript Object Notation – Remote Procedure Call) is a standard for remote procedure call, allowing developers to communicate with remote servers over HTTP. In this context, we will be using the JSON-RPC protocol to interact with the Ethereum blockchain.
Which library must I use for JSON?
There are several libraries available for working with JSON in C++. Here are a few options:
jsoncpp: A lightweight and modern JSON parser and generator.
boost::json: A popular and feature-rich JSON parsing and generating library.
glib-2.x: A modern C++ bindings for the glib JSON library.
For this example, we will use the jsoncpp library. You can install it using your package manager or by including the following line in your CMakeLists.txt file:
add_library(jsoncpp_json cpp_json.cpp)
How to use RPC of bitcoind or bitcoin-cli?
Here is an example of how you can use the JSON-RPC protocol with Bitcoin:
- bitcoind: You can use the
-jsonrpcoption when startingbitcoin-cli. For example:
./bitcoin-cli -jsonrpc=1 -url
This will start a new connection to the Bitcoin node at and you can send JSON-RPC requests to it.
- bitcoin-cli: You can also use the-jsonrpc
option when runningbitcoin-cli. For example:
bitcoin-cli -jsonrpc=1 -url
How to use RPC of Electrum API?
Here is an example of how you can use the JSON-RPC protocol with Electrum:
- Electrum
: You can start a new connection to the Electrum node at and then send JSON-RPC requests to it using the following code:
#include
#include
int main() {
// Start a new connection to the Electrum node
std::cout << "Connected to Electrum..." << std::endl;
// Send a JSON-RPC request to get all pending transactions
std::string json = "{\"method\":\"listtransactions\",\"params\":[],\"jsonrpc\":\"1.0\",\"id\":null}";
int result = json.cpp2json(json, json);
if (result == 0) {
for (int i = 0; i < result; ++i) {
std::cout << "Transaction " << i + 1 << ": " << json.cpp2string(result[i]) << std::endl;
}
}
return 0;
}
This code sends a JSON-RPC request to listtransactions with no parameters, and prints out the list of pending transactions.
Example Use Cases
- Ethereum: You can use the JSON-RPC protocol to interact with the Ethereum blockchain by sending requests to the contract’s ABI (Application Binary Interface) to execute functions.
- Bitcoin: You can use the JSON-RPC protocol to get information about the Bitcoin network, such as block timestamps and transaction counts.
- Electrum: You can use the JSON-RPC protocol to retrieve a list of pending transactions on the Electrum node.
Conclusion
In this article, we have covered how to use the JSON-RPC protocol in C++ to interact with the Ethereum blockchain. We have also provided examples of using RPC libraries for Bitcoin and Electrum API. With this knowledge, you can start building your own applications that utilize the JSON-RPC protocol to interact with these blockchains.
