Ethereum: Using JSON-RPC in C++ on Linux
In this article, we will walk you through how to use the JSON-RPC protocol in C++ to interact with the Ethereum blockchain. We will also look at how to use the RPC libraries for Bitcoin and provide examples of using the Electrum API.
What is JSON-RPC?
JSON-RPC (JavaScript Object Notation – Remote Procedure Call) is a remote procedure call standard that allows developers to communicate with remote servers over HTTP. In this context, we will use the JSON-RPC protocol to interact with the Ethereum blockchain.
Which library should I use for JSON?
There are several libraries available for working with JSON in C++. Here are some options.
- “jsoncpp”: A lightweight and modern JSON parser and generator.
boost::json: A popular and feature-rich JSON parsing and generation library.
glib-2.x: A modern C++ binding for the glib JSON library.
In 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 bitcoind or bitcoin-cli for RPC?
Here is an example of how you can use the JSON-RPC protocol with Bitcoin:
- bitcoind: When you start bitcoin-cli, you can use the "-jsonrpc" option. 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: When you start bitcoin-cli, you can also use the "-jsonrpc" option. For example:
bitcoin-cli -jsonrpc=1 -url
How to use Electrum API RPC?
Here is an example of how you can use the JSON-RPC protocol with Electrum:
- Electrum
: You can create a new connection to an Electrum node at and then send JSON-RPC requests to it using the following code:
#include
#include
int main() {
// Start a new connection to an 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 a list of pending transactions.
Use Case Examples
- Ethereum: You can use the JSON-RPC protocol to interact with the Ethereum blockchain by sending requests to the ABI (Application Binary Interface) of a contract to execute functions.
- Bitcoin: You can use the JSON-RPC protocol to obtain 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 an 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 the RPC libraries for the Bitcoin and Electrum APIs. With this knowledge, you can start building your own applications that use the JSON-RPC protocol to interact with these blockchains.