RPC stands for Remote Procedure Call. It’s a method used in programming to request a service or information from another computer or server, usually over the internet. Instead of running a function or process locally (on your own machine), you make a request to another machine to do it for you and send back the result.

In simpler terms, imagine you’re sending a message to a server asking it to perform a task and return the result, without you needing to understand how it’s done behind the scenes.

Role of RPC in Crypto:

In the world of cryptocurrency and blockchain, RPCs are crucial for communication between decentralized applications (dApps), wallets, or other blockchain tools and the blockchain itself. Here's how they work and why they are important:

1. Interacting with Blockchain Nodes

Blockchains are essentially distributed networks of nodes (computers). These nodes store the entire history of the blockchain, validate transactions, and update the network. To interact with the blockchain (like sending transactions, querying data, or deploying smart contracts), you need to communicate with one of these nodes.
RPCs act as the bridge between your application and the blockchain. For instance, if you want to check your cryptocurrency balance or send some crypto to someone, your wallet or dApp will use an RPC to send this request to a node, which will process it and return the necessary data or complete the transaction.

2. Retrieving Blockchain Data

Using an RPC, you can request data such as transaction history, wallet balances, block information, or smart contract details from the blockchain. For example, if you open your crypto wallet and it shows how much Bitcoin or Ether you have, it likely made an RPC call to the blockchain to retrieve your account balance.
The blockchain itself doesn't send you notifications or updates automatically. It’s the RPC call that fetches the required information every time your wallet or app needs it.

3. Sending Transactions

When you send cryptocurrency to another person or interact with a smart contract, this is essentially a transaction. For this to be processed on the blockchain, your wallet or dApp sends an RPC request to a node. The node then broadcasts your transaction to the network, where it will be validated and included in the next block.
Without RPCs, there wouldn’t be an easy way to submit transactions to the blockchain from your device.

4. Smart Contract Interactions

Smart contracts are automated programs that run on the blockchain. When dApps or users want to trigger a smart contract function (like trading tokens on a decentralized exchange), they make an RPC call to the blockchain. The node processes the request, interacts with the smart contract, and sends back the results.
For example, if you’re using a decentralized finance (DeFi) app to swap tokens, your request goes through an RPC call to interact with the smart contract that handles the swap.

Why RPCs Matter in Crypto:

• Accessibility: They make it easier for developers and users to interact with the blockchain without running a full node themselves. Full nodes are heavy and require lots of computing power and storage, so RPCs allow users to connect to the blockchain without this burden.
• Efficiency: RPCs provide a faster and more efficient way to access blockchain data and send transactions.
• Security: By connecting to trusted nodes via RPC, users and dApps can securely interact with the blockchain without having to trust third-party applications.

Connecting to RPCs from Wallets

When using a cryptocurrency wallet, whether it's a software wallet like MetaMask or a hardware wallet like Ledger, your wallet needs to communicate with the blockchain network to perform tasks such as sending transactions, checking balances, or interacting with smart contracts. This communication happens through Remote Procedure Calls (RPCs), which act as the bridge between your wallet and the blockchain nodes.

1. What is an RPC (Remote Procedure Call)?

RPC is a communication protocol that allows your wallet to send requests to a blockchain node (a server running a full copy of the blockchain) and receive responses. In the context of blockchain, RPCs are used to:

• Query data from the blockchain (e.g., balance of an address).
• Submit transactions to the network.
• Interact with smart contracts.

In simple terms, RPCs are like a messenger. They take your request (e.g., check balance) from the wallet, forward it to a node on the blockchain, and bring back the result.

2. Why Do Wallets Need to Connect to RPCs?

Wallets need real-time data from the blockchain to provide useful functionality, such as:

• Checking balances of cryptocurrencies.
• Viewing transaction history.
• Sending or signing transactions.
• Interacting with decentralized applications (dApps) or smart contracts.

Wallets don't run full blockchain nodes on your device, as that would be too resource-intensive. Instead, they connect to existing nodes via RPCs to interact with the blockchain.

3. How Wallets Connect to RPCs

Step 1: Choosing a Node (RPC Endpoint)
A node is a computer that participates in the blockchain network, maintaining a copy of the blockchain and processing transactions. Wallets are configured to connect to specific nodes using an RPC endpoint. An RPC endpoint is simply a URL or IP address where a blockchain node can be accessed.
Example of an Ethereum RPC endpoint: https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID. Wallets like MetaMask, Trust Wallet, or Phantom (for Solana) come pre-configured with RPC endpoints for different blockchains like Ethereum, Binance Smart Chain, or Solana.

Step 2: Sending RPC Requests
The wallet uses the RPC endpoint to communicate with the node. Common types of requests include:

• Get Balance: Asking the node for the balance of a particular address.
• Send Transaction: Broadcasting a signed transaction to the blockchain for validation.
• Call Smart Contract Method: Querying a smart contract’s state or executing a function on the contract.

Wallets make these requests through simple HTTP or WebSocket connections. The request follows a specific format (typically JSON-RPC), and the node responds with the requested data.

Example: Checking Ethereum Balance

                        {
                          "jsonrpc": "2.0",
                          "method": "eth_getBalance",
                          "params": ["0xYourAddress", "latest"],
                          "id": 1
                        }
                      

Step 3: Receiving and Displaying Responses
Once the blockchain node processes the request, it sends a response back to the wallet. For example, when checking an Ethereum balance, the node returns the balance in wei. The wallet converts this raw data into a user-friendly format (like ETH or USD) and displays it in the interface.

Customizing RPC Endpoints in Wallets
Wallets often allow users to change the default RPC endpoints. This can be useful if a user wants to:

• Connect to a private or local node.
• Use a different provider (e.g., switching from Infura to Alchemy).
• Improve performance (some RPCs may be faster than others).

In MetaMask, you can add custom RPC endpoints by going to "Settings > Networks" and configuring a new network.

4. Security Considerations

Using trusted RPC endpoints is important, as malicious or unreliable nodes could return incorrect data or even try to compromise transactions. Most popular wallets use well-known providers like Infura, Alchemy, or Binance to connect to their blockchains.

5. Connecting via WebSockets

For real-time updates (e.g., receiving transaction confirmations as they happen), wallets may use WebSockets instead of HTTP. WebSockets allow the node to push new data to the wallet as soon as it becomes available, without the wallet needing to constantly poll the node for updates.