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A Complete Guide of RPC (Remote Procedure Call)

What is RPC (Remote Procedure Call)?

🔹 What is RPC (Remote Procedure Call)?

Remote Procedure Call (RPC) is a protocol that allows a computer program to execute a function or procedure on another computer (remote server) as if it were a local function.

Key Idea: RPC enables communication between different processes across a network or within the same system.
Used In: Microservices, Distributed Systems, API Communication, Cloud Computing.


🔹 How Does RPC Work?

1️⃣ Client sends a request → Calls a function on a remote server.
2️⃣ Server processes the request → Executes the function.
3️⃣ Server sends a response → Returns the output to the client.

📌 Example of RPC Flow:

Client App  ── Request (RPC Call) ──> Remote Server  
Remote Server  ── Process & Execute ──> Send Response  
Client App  ── Receive & Process Response ──> Done ✅

🔹 Types of RPC

1️⃣ Synchronous RPC

  • Client waits for the server to respond before continuing.
  • Example: Traditional API calls (like REST).

2️⃣ Asynchronous RPC

  • Client does not wait for a response, allowing parallel execution.
  • Example: Event-driven microservices.

🔹 RPC vs. REST API

FeatureRPCREST API
ProtocolCan use HTTP, TCP, UDP, gRPC, etc.Uses HTTP
Data FormatBinary (Protocol Buffers, Thrift, Avro) or Text (JSON, XML)JSON/XML
PerformanceFaster (Binary format + Compression)Slower due to HTTP overhead
Streaming SupportYes (gRPC, Thrift, WebSockets)Limited (Needs WebSockets)
Use CaseMicroservices, High-Performance APIsWeb & Mobile APIs

🔹 Popular RPC Frameworks

RPC FrameworkUsed ForProtocol
gRPCMicroservices, Cloud APIsHTTP/2 + Protocol Buffers
Apache ThriftHigh-speed RPCsBinary Protocol, TCP
JSON-RPCWeb APIsHTTP + JSON
XML-RPCLegacy systemsHTTP + XML

🔹 Example of RPC Call

Using gRPC (Google RPC) in Python:

import grpc
import example_pb2
import example_pb2_grpc

channel = grpc.insecure_channel('localhost:50051')
stub = example_pb2_grpc.GreeterStub(channel)
response = stub.SayHello(example_pb2.HelloRequest(name='Alice'))
print(response.message)
Code language: JavaScript (javascript)

This sends an RPC request to a server and gets a response.


🎯 When to Use RPC?

✅ When high-speed communication is needed (Microservices, Cloud).
✅ When APIs must support streaming & multiplexing (gRPC).
✅ When services need to communicate in different programming languages.

What is an RPC Framework?

🔹 What is an RPC Framework?

An RPC (Remote Procedure Call) framework is a set of tools, libraries, and protocols that allow applications to execute functions or procedures on a remote server as if they were local functions.

Purpose: Simplifies communication between distributed systems, microservices, and cloud applications.
Example Use Case: A frontend app calling a backend function on a remote server without worrying about networking details.


🔹 How Does an RPC Framework Work?

1️⃣ Client makes an RPC request (calls a function remotely).
2️⃣ RPC framework serializes the request (converts data into a transportable format).
3️⃣ Server receives and processes the request.
4️⃣ RPC framework deserializes the response and returns it to the client.

📌 Example of an RPC Call Flow:

Client  ──> RPC Framework ──> Network ──> Server  
Client  <── RPC Framework <── Network <── Server Response

💡 Think of it like calling a function, but it runs on another server! 🚀


🔹 Popular RPC Frameworks

RPC FrameworkUsed ForProtocolSerialization Format
gRPCMicroservices, Cloud APIsHTTP/2Protocol Buffers (ProtoBuf)
Apache ThriftCross-language RPCTCP, HTTPCompact Binary Format
JSON-RPCWeb APIs, JavaScript-based AppsHTTP, WebSocketsJSON
XML-RPCLegacy SystemsHTTPXML
ZeroMQ (ØMQ)High-performance messagingCustom (No built-in protocol)Custom
DaprCloud-Native ApplicationsHTTP/gRPCJSON/ProtoBuf

🔹 Why Use an RPC Framework?

Simplicity → Developers call remote functions like local functions.
High Performance → Many frameworks (like gRPC) use binary serialization for fast data transmission.
Cross-Language Support → Works across different programming languages (e.g., Python client calling a Go server).
Streaming Support → Some frameworks (e.g., gRPC) support bidirectional streaming.


🔹 gRPC Example (Python)

Define an RPC Service (hello.proto):

syntax = "proto3";

service Greeter {
  rpc SayHello (HelloRequest) returns (HelloReply);
}

message HelloRequest {
  string name = 1;
}

message HelloReply {
  string message = 1;
}
Code language: JavaScript (javascript)

✅ The RPC framework handles serialization, networking, and responses automatically!


🎯 Final Thoughts

🔥 An RPC framework helps build high-performance distributed systems efficiently! 🔥
Best for: Microservices, Cloud APIs, and High-Speed Communication.
Best choice: gRPC for modern systems, Thrift for cross-language, and JSON-RPC for web apps.

Difference Between RPC and RPC Framework

AspectRPC (Remote Procedure Call)RPC Framework
DefinitionA concept that allows calling functions on a remote server as if they were local.A set of tools, libraries, and protocols that implement RPC functionality.
FunctionalityEnables communication between client and server in distributed systems.Provides ready-to-use implementations for handling RPC calls, serialization, security, and networking.
Example ConceptA client requests a function (getUserDetails()) on a remote server.A framework like gRPC, Apache Thrift, or JSON-RPC handles the networking, serialization, and execution of getUserDetails().
Transport MechanismCan work over HTTP, TCP, UDP, WebSockets, etc.Uses specific transport mechanisms like HTTP/2 (gRPC), TCP (Thrift), or HTTP (JSON-RPC).
SerializationRequires a way to encode and decode data (e.g., JSON, XML, Binary).Built-in serialization formats like ProtoBuf (gRPC), JSON (JSON-RPC), or Binary (Thrift).
SecurityMust be implemented separately (e.g., authentication, encryption).Many frameworks provide built-in TLS encryption, authentication, and access control.
Cross-Language SupportRequires manual implementation for different languages.Provides auto-generated client and server code for multiple languages (e.g., Python, Java, Go, C++).

How RPC Works (Conceptually)?

1️⃣ Client Calls a Function

  • A client program calls a function (getUserDetails()) that is actually located on a remote server.

2️⃣ Request Serialization

  • The function call’s parameters (data) are converted into a format that can be transmitted over a network (e.g., JSON, Protocol Buffers, XML, Binary).

3️⃣ Network Transmission

  • The serialized data is sent over a network (via HTTP, TCP, UDP, WebSockets, etc.).

4️⃣ Server Receives the Request

  • The server’s RPC system deserializes the request and calls the actual function on the server.

5️⃣ Function Execution & Response

  • The server executes the function (getUserDetails()) and sends the response back to the client.

6️⃣ Client Receives the Response

  • The client deserializes the response and continues execution as if the function ran locally.

📌 RPC Conceptual Flow:

pgsqlCopyEditClient ───> (Serialize Data) ───> Network ───> Server  
Server ───> (Execute Function) ───> Return Response ───> Client  

🔹 RPC vs. Normal Function Calls

FeatureLocal Function CallRemote Procedure Call (RPC)
Execution LocationRuns on the same machineRuns on a remote server
Data PassingDirect memory accessData is serialized and sent over the network
PerformanceFast (no network delay)Slower (network latency)
ComplexitySimpleRequires handling network failures, serialization, security
Use CaseLocal programsMicroservices, Cloud APIs, Distributed Systems

🔹 Real-World Use Cases of RPC

Microservices Communication → Services talk to each other in cloud-native applications.
Database Requests → Clients call database functions remotely.
Remote System Administration → Commands are executed on remote servers.
Game Servers & Multiplayer Apps → Actions from one player affect other players over a network.

🔹 List of All Popular RPC Frameworks

RPC frameworks simplify remote function execution by handling networking, serialization, and security. Below is a list of widely used RPC frameworks categorized based on their use cases.


1️⃣ Modern High-Performance RPC Frameworks

FrameworkDescriptionProtocolSerialization FormatBest For
gRPCGoogle’s high-performance RPC frameworkHTTP/2Protocol Buffers (ProtoBuf)Microservices, Cloud APIs
Apache ThriftCross-language RPC systemTCP, HTTPCompact Binary, JSON, Simple JSONLarge-scale distributed systems
Cap’n ProtoHigh-speed serialization and RPCCustom (No extra encoding needed)Cap’n Proto (Zero Parsing Overhead)Low-latency systems
DaprCloud-native distributed application runtimeHTTP, gRPCJSON, ProtoBufMicroservices & Kubernetes

2️⃣ Web-Based RPC Frameworks

FrameworkDescriptionProtocolSerialization FormatBest For
JSON-RPCLightweight RPC using JSON over HTTP/WebSocketsHTTP, WebSocketsJSONWeb applications, JavaScript-based systems
XML-RPCSimple RPC protocol using XML over HTTPHTTPXMLLegacy systems
WAMP (Web Application Messaging Protocol)Web-based RPC with real-time pub/subWebSockets, TCPJSON, MsgPack, CBORWebSockets-based APIs
FalcorNetflix’s RPC for efficient data fetchingHTTPJSONWeb applications

3️⃣ Messaging-Based RPC Frameworks

FrameworkDescriptionProtocolSerialization FormatBest For
ZeroMQ (ØMQ)High-performance messaging libraryTCP, IPC, MulticastCustomLow-latency, real-time systems
Apache AvroSchema-based RPC with a focus on Big DataTCP, HTTPAvro Binary, JSONBig Data, Streaming (Kafka, Hadoop)
MessagePack-RPCLightweight binary-based RPCTCP, UDPMessagePackIoT & high-performance applications
NanomsgSimplified version of ZeroMQTCP, IPCCustomHigh-speed messaging

4️⃣ Enterprise & Legacy RPC Frameworks

FrameworkDescriptionProtocolSerialization FormatBest For
CORBA (Common Object Request Broker Architecture)Classic RPC framework for enterprise systemsIIOP (TCP-based)Binary (IDL-based)Legacy enterprise applications
RMI (Remote Method Invocation)Java’s built-in RPC mechanismJRMP (Java Remote Method Protocol)Java SerializationJava-based distributed applications
HessianLightweight binary-based RPCHTTPHessian Binary FormatJava & cross-platform systems
TARSTencent’s distributed RPC frameworkTCP, HTTPTARS, ProtoBuf, JSONLarge-scale microservices

5️⃣ Blockchain & Decentralized RPC Frameworks

FrameworkDescriptionProtocolSerialization FormatBest For
Ethereum JSON-RPCRPC API for Ethereum blockchainHTTP, WebSocketsJSONBlockchain applications
Bitcoin RPCRPC interface for Bitcoin nodesHTTPJSONCryptocurrency development

🔹 Choosing the Right RPC Framework

Use CaseRecommended Framework
Microservices & CloudgRPC, Thrift, Dapr
Web-Based RPCJSON-RPC, WAMP, Falcor
Big Data & StreamingApache Avro, MessagePack-RPC
Low-Latency & High-PerformanceZeroMQ, Cap’n Proto
Enterprise & Legacy AppsCORBA, RMI, Hessian
Blockchain AppsEthereum JSON-RPC, Bitcoin RPC

🎯 Final Thoughts

If you need a high-performance modern RPC framework, use gRPC or Apache Thrift.
For web-based applications, JSON-RPC is a lightweight option.
For low-latency, high-speed messaging, ZeroMQ or Cap’n Proto are great choices.
For distributed systems and big data, Apache Avro is recommended.

🔹 Default RPC Methods in Different Scenarios

Below is a breakdown of what happens by default when you call a remote function in different environments.

ScenarioWhat Happens By Default?Default RPC Framework
PHP in XAMPP (Apache Server)No native RPC; you must use JSON-RPC, SOAP, or REST❌ None (you must specify)
Java Calling Remote FunctionsUses Java RMI (Remote Method Invocation)Java RMI
Python Calling a Remote FunctionUses built-in xmlrpc.client for XML-RPCXML-RPC
Node.js Communicating with Remote ServicesTypically uses HTTP API calls (REST)HTTP (REST)
.NET / C# Calling Remote ServicesUses WCF (Windows Communication Foundation)WCF (SOAP/XML-RPC)
C++ Distributed SystemsUses CORBA (Common Object Request Broker Architecture)CORBA
Web Browsers Calling Remote FunctionsUses AJAX (JavaScript HTTP Requests)REST over HTTP (AJAX, Fetch API)
Linux System CallsUses gRPC or DBus for inter-process communicationgRPC, DBus
Blockchain Smart Contracts (Ethereum, Bitcoin, etc.)Uses JSON-RPC to communicate with nodesJSON-RPC
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