PetstoreAPI Socket.IO Protocol Guide

Modern Petstore API provides Socket.IO support for real-time, bidirectional communication with automatic fallback to HTTP long-polling when WebSocket is unavailable. Our Socket.IO implementation powers the customer support chat system at wss://api.petstoreapi.com, featuring room-based messaging, automatic reconnection, broadcast capabilities, and seamless fallback for environments that don't support WebSocket.

Overview

Protocol: WebSocket with automatic HTTP long-polling fallback

Communication: Bidirectional (Client ↔ Server)

Endpoint: wss://api.petstoreapi.com

When to Use Socket.IO:

✅ Real-time features that must work everywhere

✅ Customer support chat systems

✅ Need automatic fallback when WebSocket unavailable

✅ Room-based messaging

✅ Broadcast capabilities

When NOT to Use Socket.IO:

❌ You need raw WebSocket (use WebSocket protocol instead)

❌ Simple server → client updates (use SSE instead)

How Socket.IO Works

Client                                    Server
  │                                         │
  ├───────── WebSocket Connection ─────────>│
  │          (or falls back to polling)      │
  │                                         │
  ├───────── joinChat (room) ─────────────>│
  │<──────────── connected ─────────────────┤
  │                                         │
  ├───────── chatMessage ─────────────────>│
  │<───────── chatMessage (broadcast) ─────┤
  │                                         │

Key Features:

Automatic reconnection

Room-based messaging

Broadcast to multiple clients

Automatic fallback to HTTP long-polling

Binary data support

Connection

JavaScript (Browser)

JavaScript (Node.js)

Python (python-socketio)

Customer Support Chat

Join Chat Room

Send Chat Message

Receive Messages

Agent Assignment

Typing Indicators

Send Typing Started

Send Typing Stopped

Receive Typing Indicators

Rooms

Join a Room

Leave a Room

Send to Room

Advanced Usage

Reconnection Management

Message Acknowledgment

Binary Data

Error Handling

Connection Errors

Message Errors

Best Practices

1. Cleanup on Disconnect

2. Message Queue

3. Rate Limiting

Troubleshooting

Connection Fails

Check authentication token

Verify server URL

Check browser console for CORS errors

Try enabling polling transport

Not Receiving Messages

Verify you've joined the correct room

Check event name matches exactly

Ensure socket is connected

Check server logs for errors

High Memory Usage

Clean up event listeners

Don't store entire message history

Disconnect when not needed

Comparison with WebSocket

Feature	Socket.IO	WebSocket
Fallback	✅ HTTP polling	❌ No fallback
Reconnection	✅ Automatic	⚠️ Manual
Rooms	✅ Built-in	⚠️ Manual
Broadcasting	✅ Built-in	⚠️ Manual
Binary Support	✅ Yes	✅ Yes
Library Required	✅ Yes	❌ Native
Overhead	Medium	Low

Choose Socket.IO when:

You need fallback mechanisms

Building chat/collaboration features

Want built-in room/broadcast support

Choose WebSocket when:

Maximum performance needed

Want native browser support

Building custom protocol

Interactive Documentation

API Specification: AsyncAPI 3.0

Protocol Overview: All Protocols

WebSocket Guide: WebSocket Protocol

WebSocket Guide - Native WebSocket protocol

SSE Guide - Server-sent events for streaming

Quick Start Guide

Overview#

How Socket.IO Works#

Connection#

JavaScript (Browser)#

JavaScript (Node.js)#

Python (python-socketio)#

Customer Support Chat#

Join Chat Room#

Send Chat Message#

Receive Messages#

Agent Assignment#

Typing Indicators#

Send Typing Started#

Send Typing Stopped#

Receive Typing Indicators#

Rooms#

Join a Room#

Leave a Room#

Send to Room#

Advanced Usage#

Reconnection Management#

Message Acknowledgment#

Binary Data#

Error Handling#

Connection Errors#

Message Errors#

Best Practices#

1. Cleanup on Disconnect#

2. Message Queue#

3. Rate Limiting#

Troubleshooting#

Connection Fails#

Not Receiving Messages#

High Memory Usage#

Comparison with WebSocket#

Interactive Documentation#

Related Resources#