RPCs vs. APIs: A Simple Guide

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1 Feb 2024

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January 30, 2024
If you're looking to build applications on the blockchain, you'll need to understand and use RPCs (Remote Procedure Calls) and APIs (Application Programming Interfaces). These two technologies are essential for interacting with the blockchain network and accessing its data.

Let’s take a closer look at what RPCs and APIs are, how they work, and their role in Web3. We'll also explore some real-world examples of RPCs and APIs in action, as well as their significance in the world of Web3.

Let's start with RPCs. RPC stands for Remote Procedure Call. At its core, an RPC is a type of communication protocol that lets one computer or program request a service or function from another computer/program over a network.
Here's how it works 👇
The requester (e.g., your computer or smartphone) sends a request to the receiver (e.g., another computer on the same network or even across the internet). The receiver processes that request and responds with the requested information.
This process enables devices or programs to communicate with each other remotely. A simple analogy would be calling customer support for assistance - you make a call requesting help, and the support representative provides you with relevant information.
Examples of RPC protocols include NFS (Network File System), D-Bus, SORCER, XML-RPC, JSON-RPC, etc. These protocols allow different systems to communicate effectively by standardizing their interactions.
Now that we've covered what an RPC is, let's see how they relate to Web3.

In Web3, nodes play an important role in facilitating communication between dApps (decentralized applications) and smart contracts. Nodes enable this function through Remote Procedure Calls (RPC), which connect dApps to the blockchain.
For example, when using an Ethereum dApp, you can use the JSON-RPC protocol to make RPC requests through an Ethereum node. This allows your dApp to access and interact with the Ethereum blockchain, retrieve data, send transactions, and execute smart contracts.
In this context:

Your dApp is the client.
The Ethereum node is the server.
The JSON-RPC protocol specifies methods for making calls to the Ethereum node (server) in order to request data or perform actions on the blockchain.

By leveraging RPCs in Web3 technology, dApps can seamlessly connect and interact with blockchains. You've now seen how RPCs work both generally and specifically within Web3. Let's move on to APIs.

Next up are APIs. An API is a set of rules and protocols that allows different software applications or systems to communicate with each other. It defines how different components of a system should interact and exchange information.
An API acts as a bridge between two different systems or applications by providing a standard way for them to exchange data and services. APIs specify:

The types of requests that can be made.
The format of those requests.
The data that will be returned in response to those requests.

For example, when using Google Maps on your smartphone, you're essentially using Google's
mapping service through its API. You send location coordinates from your phone (request), which then retrieves relevant map data from Google's database (response).
Many companies provide public APIs so that developers can integrate their services into their applications easily. Examples include social media platforms like Twitter and Facebook and payment gateways like PayPal or Stripe. These companies offer a set of API endpoints that developers can use to access their data or services, such as retrieving user information, posting tweets, and processing payments.

In the context of Web3 and blockchain technology, APIs play a crucial role in enabling integration between different applications and services. They allow dApps and other software systems to interact with blockchain networks and access their data or functionalities.
For example, when building a dApp that involves processing cryptocurrency payments using Ethereum (ETH), you might use the web3.js library - an API for Ethereum development. This library provides easy-to-use methods for interacting with the Ethereum network, such as sending transactions, querying account balances, deploying smart contracts, etc.
In this scenario, the web3.js library acts as an API. Your dApp uses the library's methods to communicate with the Ethereum network. Through these methods, you can send payment requests to the network, and the network processes those requests based on its rules and consensus mechanisms.
Once processed, the transaction is recorded on the blockchain, and the recipient receives the payment. This demonstrates how APIs enable communication between dApps and blockchain networks in Web3 technology.
Let's take a look at some examples that illustrate these concepts further.

Now that we've covered the basics, let's explore some real-world examples to illustrate how RPCs and APIs work in practice.

Example 1: Sending a Transaction on Ethereum Using RPC

Suppose you want to send a transaction on the Ethereum network using an RPC.
Here's what happens:

You use the eth_sendTransaction method of JSON-RPC to create and sign a transaction locally.
Then, you send this signed transaction as an RPC request to an Ethereum node.
The node processes your request, verifies your signature, and broadcasts the transaction to the network.
Miners then include your transaction in a block, which is added to the blockchain once it's validated by other nodes.

This example illustrates how you can use an RPC to interact with the Ethereum network and perform actions such as sending transactions.

Example 2: Retrieving Token Prices Using APIs

Another example involves retrieving token prices from a cryptocurrency exchange using its API. Let’s say you're building a dApp that displays real-time token prices.
Here's what happens:

You make an HTTP request to one of the exchange's API endpoints (e.g., https://api.exchange.com/prices).
In this request, you specify:
1. The type of data you want (e.g., token prices).
2. Any additional parameters required by the endpoint (e.g., token symbols).
The exchange processes your request, retrieves token prices from its database or another source, and returns them as an HTTP response in JSON format.

You can then parse and display this data within your dApp's user interface. This example demonstrates how you can use APIs to integrate external data sources into your dApp and provide users with real-time information.
These examples illustrate the practical applications of RPCs and APIs in Web3 technology, including interacting with blockchain networks, sending transactions, retrieving on-chain or off-chain data, and integrating services from cryptocurrency exchanges or other platforms into your dApps.

Simply put, RPCs and APIs are essential for enabling communication between various components of Web3 technology. However, relying solely on RPC nodes and public APIs can have its drawbacks, such as service disruptions, centralization, and rate limits.
This is where Syntropy comes in. By providing a decentralized way to access real-time on-chain data directly from the mempool, Syntropy’s streaming oracle can enhance the efficiency and effectiveness of Web3 applications. It eliminates reliance on centralized infrastructure while also offering a more secure and reliable solution compared to traditional RPCs and APIs.
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