JSON (JavaScript Object Notation) is a lightweight data interchange format that can represent numbers, strings, sequences, and collections of name/value pairs.
JSON-RPC is a stateless, lightweight remote procedure call (RPC) protocol. This specification defines its data structures and processing rules while remaining transport-agnostic - suitable for intra-process communication, sockets, HTTP, or various messaging environments. The protocol utilizes JSON (RFC 4627) as its data format.
Core Concepts
- JSON-RPC Specification: Defines request/response structures for remote procedure calls
- Transport Independence: Works over HTTP, WebSockets, or other message-passing systems
- Pub/Sub Support: Experimental implementations available in Geth 1.4+ and Parity 1.6+
Client Endpoints
Default JSON-RPC endpoints across major Ethereum clients:
| Client | Default Endpoint |
|---|---|
| Geth | http://localhost:8545 |
| Parity | http://localhost:8545 |
| C++ | http://localhost:8545 |
| Python | http://localhost:4000 |
Client-Specific Configuration
Geth Configuration
Enable JSON-RPC with HTTP transport:
geth --rpcCustomize listening address/port:
geth --rpc --rpcaddr 0.0.0.0 --rpcport 8079Enable CORS for web applications:
geth --rpc --rpccorsdomain "http://yourdomain.com"👉 Learn advanced Geth configuration strategies
C++ Configuration
Basic RPC activation:
./eth -jPort customization:
./eth -j --json-rpc-port 8079Python Configuration
Default endpoint runs on 127.0.0.1:4000. Customize with:
pyethapp -c jsonrpc.listen_port=4002 -c jsonrpc.listen_host=127.0.0.2 runBest Practices
- Security: Never expose RPC endpoints to public networks without authentication
- Performance: Limit batch request sizes to avoid timeouts
- Monitoring: Track API usage metrics to identify performance bottlenecks
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Frequently Asked Questions
Q: What's the difference between JSON-RPC and Web3.js?
A: JSON-RPC is the underlying protocol, while Web3.js is a JavaScript library that provides convenient methods for interacting with JSON-RPC endpoints.
Q: Can I use JSON-RPC for real-time event monitoring?
A: Yes, through the experimental pub/sub support in Geth and Parity, though production systems should consider dedicated event indexing services.
Q: How do I secure my JSON-RPC endpoint?
A: Implement IP whitelisting, authentication, and consider using reverse proxies with HTTPS termination.
Q: What performance considerations exist for JSON-RPC?
A: Large batch requests or complex filter queries can significantly impact node performance. Consider query optimization and rate limiting.
Q: Are there alternatives to JSON-RPC for Ethereum interaction?
A: Yes, GraphQL endpoints are becoming available as an alternative query language for blockchain data.
Q: How can I debug JSON-RPC requests?
A: Most clients support verbose logging modes, and tools like Postman or curl can be used to manually test endpoints.