What is JSON-RPC in Ethereum?

JSON-RPC is used to communicate with an application that you running on your computer. It uses the HTTP protocol for remote procedure calls and JSON for data representation. It’s a stateless, lightweight RPC protocol that’s written in JavaScript. For example, JSON-RPC makes communication between client and server simpler and easier to implement than Java Server Pages (JSP) or XML Web Services. Because JSON-RPC relies on HTTP, it doesn’t require you to run a separate web server. One just needs to have at least one web browser with a connection to the internet.

What is JSON-RPC?

• JSON-RPC is a remote procedure call protocol encoded in JSON and uses HTTP requests, forming a bridge between the web programming languages and the Ethereum blockchain.
• The implementation of the JSON-RPC interface will consist of an HTTP JSON API or can be pushed by an Ethereum node through IPC (Inter-Process Communication). The contents of all data requests from clients are parsed as JSON objects and constructed into responses with serialized data.
• The client for executing RPC queries doesn’t need to implement any networking layer so it can remain agnostic to how RPCs are executed, just providing a generic interface for interacting with smart contracts based on name, argument type, and value types.

What are RPCs?

• RPCs are the primary way of fetching data in a blockchain system. When new blocks are created and the old ones are updated, an RPC is needed to make sure all nodes (individual copies of the blockchain) have the same information.
• A function named getmemorypool returns the current state of the transaction pool, which includes lists of unconfirmed transactions and memory addresses with a specific amount of coins.
• An RPC function spends time with the network, as it has to wait for relaying nodes to learn about changes on other endpoints before it can process them again itself. This slows down processing speed and increases latency, but doesn’t affect the validity or security of data retrieved by an RPC call.

Client-Side Interaction

There is a need for a new approach to communication in blockchain networks. 

• The traditional model of client-server interaction entails that a client requests information from the server and then waits for the server to respond with the requested data, which is then processed by the client before continuing with its operation. 
• This model does not allow for instant response time and therefore creates delays for users trying to communicate with servers, hindering performance.
• Traditional client-server interaction also relies on static data types that do not support dynamic data models and therefore require the client to have precompiled information regarding all possible data. 
• This limits flexibility and prevents new services from being created to meet future needs.

This is where the concept of client-side interaction in blockchain comes in. A common example of this concept is a chat application that allows users to interact with each other and exchange information, while at the same time servers retain this information on their own databases. Flexibility is achieved by allowing communication between clients directly, or through message passing depending on the complexity of the operation being performed.

Local Calls vs RPC

In a blockchain, the RPC API can be used to execute transactions, and can also be used to register transactions that need to be executed in the future.

Local Calls	RPC
Local calls are faster..	RPCs are slower.
They have limitations on the number of requests sent to them over time.	They can handle larger data sets quickly and efficiently.

Why Use RPC?

RPC is a method of performing an operation using the API (Application Programming Interface) rather than using a program called command line and invoking a command script, this allows us to do tasks quicker. 

• For example, if there are billions of users and only a few dozen full nodes and all of them are currently working on processing transactions means they cannot send any new ones until they finish execution and sync with the network. 
• Suppose there is a user who wants to send funds to someone else in the network and this is when he can make use of RPC because if the full node that he sent a transaction to is currently busy with other operations it can still be submitted via RPC. 
• This can also be used by developers who want to access some information on the blockchain system in real-time for example for debugging purposes or retrieving public information about an address.

Advantages of JSON-RPC

• Simple and elegant: JSON-RPC is a simple and elegant protocol for encapsulating remote procedure calls. It was originally developed as part of the Netscape/Mozilla project but it is now widely used to communicate between browser-based applications, web services, or any other client-server communications for that matter.
• JSON-RPC has some advantages over its predecessors HTTP POST and HTTP GET:. JSON syntax is less verbose than XML and comes with a small codebase that scales well on a wide variety of platforms. The entire protocol was designed to be extensible by defining new data types in addition to operations.

Ethereum JSON-RPC

Ethereum JSON-RPC is a Universal Command Line Interface to Ethereum that provides a uniform interface over raw Weka, RPC, and Web3 connection. 

• It is an HTTP web service using JSON, which can be hooked up in any programming environment. It enables the interaction with Ethereum nodes from outside the browser environment and from within it as well.
• JSON-RPC is a simple remote procedure call protocol encoded in JSON (Extensible Markup Language), over the HTTP 1.1 protocol. The Ethereum JSON-RPC API is implemented as a set of Web3 object methods that allow clients to interact with the Ethereum blockchain.
• JSON RPC API is also used by Mist (popular Ethereum wallet), Ethereum Wallet, and several other popular wallets and applications.
• The Ethereum JSON-RPC API calls follow the pattern: TransactionHash (string, optional) – The hash of the transaction containing the contract code. If no transaction hash is provided, then contract creation will be attempted on the currently selected account.
  

Dapp Developers:  Third-Party APIs

While developers can interact with the Ethereum blockchain via the JSON-RPC API, they often prefer to build using a developer platform like Alchemy or Moralis. That’s because these developer platforms allow developers to write intuitive, one line method calls to most blockchains – they serve as wrappers for multiple (or complicated) JSON RPC calls under the hood. Depending on the developer platform, they’ll also have abstractions such as specialized APIs (e.g., NFT APIs) or SDKs to make building even easier and faster.