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The Complete Guide to Websocket Servers

Websockets provide bidirectional, full-duplex communication between clients and servers over a single TCP connection. This makes them well-suited for real-time applications such as chat, notifications, collaborations tools, IoT devices, and more.

In this comprehensive guide, we‘ll cover everything you need to know about websocket servers including:

Whether you‘re new to websockets or looking to level up your skills, this guide has you covered. Let‘s get started!

What Are Websockets and How Do They Work?

Websockets provide full-duplex communication over a single TCP connection between a client (like a web browser) and a server. This means data can flow in both directions without needing to open separate connections for each data transfer.

Once a websocket connection is established, communication happens over the same TCP socket. This avoids the overhead of HTTP where a new connection would have to be established for every request/response cycle.

Websocket communication diagram

Websocket communication remains over the same TCP socket

Some key aspects of how websockets work:

  • Communication starts with an HTTP handshake to upgrade to the websocket protocol
  • After the upgrade, data flows over TCP rather than HTTP
  • Either client or server can send data at any time rather than waiting for requests
  • The connection remains open until client or server closes it

This creates a low latency, persistent communication channel.

Differences from HTTP

Normal HTTP communication relies on clients initiating requests to which the server responds. This makes HTTP communication unidirectional and stateless.

Every request/response cycle requires establishing a new connection which introduces latency and overhead.

Websockets overcome these limitations by introducing a persistent, bidirectional communication channel. Some key differences from HTTP:

Websockets HTTP
Bidirectional Unidirectional
Low latency Higher latency
Persistent connection New connection per request
Initiated with HTTP handshake Communication always over HTTP
Messages sent over TCP socket Requests/responses over HTTP

So in summary, Websockets reduce overhead and latency by establishing a two-way communication channel over TCP rather than relying on HTTP request/response cycles.

Benefits of Using Websockets

Here are some of the key benefits that make websockets useful compared to HTTP:

1. Low latency

There is very low latency since once the handshake is complete, data flows directly over TCP rather than HTTP. This avoids roundtrips to establish separate connections.

2. Great for real-time apps

The bidirectional nature and low overhead allow websockets to enable real-time capabilities for apps like chat, live updates, notifications etc.

Servers can instantly push new data instead of waiting for client requests.

3. Persistent connections

Sockets allow long lived connections rather than opening and closing connections. This avoids expensive connection establishment costs.

4. Efficiency

With no need to establish separate connections or handle request/response cycles, less bandwidth is used overall.

5. Flexibility

Websockets work well alongside HTTP rather than needing to build an entire architecture around them. You can elegantly fall back to HTTP methods.

Use Cases for Websockets

Here are some of the most common use cases where websockets thrive:

Real-time apps

Chat apps, real-time collaboration platforms, live sports updates etc benefit hugely from instant data pushes.

Multiplayer browser games

Fast communication enables compelling multiplayer experiences with lower latency.

Financial apps

Live stock tickers, real-time trading platforms require fast data flows that HTTP cannot match.

IoT and devices

Connecting and coordinating devices and sensors that may send lots of data.

Notifications

Instantly notify users of events rather than constant polling. Useful for social media, email and more.

Control interfaces

Remotely control devices, presentations and more with lower latency.

Monitoring

Dashboards that show real-time progress, metrics and logs as they occur.

How to Choose a Websocket Server

When choosing a websocket server, here are some key criteria to evaluate:

Criteria Description
Self-hosted vs Managed Do you want to host and manage it yourself or use a fully managed service?
Features Authentication, clustering, message queues – which features do you need?
Performance Throughput, scalability and latency capabilities
Ease of use How easy is it to deploy, configure and update?
Cost One time license? Usage based pricing? Free open source?
Supported platforms/languages Node, Java, C# or other platforms?

Self-Hosted vs Managed Services

A key decision is whether you want to operate your own websocket server or use a fully managed platform.

Self-hosted pros:

  • Complete control
  • Customize technology stack
  • Avoid ongoing costs
  • Scale yourself on your cloud platform

Managed services pros:

  • Faster time-to-market
  • Automatic scaling and uptime
  • Additional features like auth, message queues etc
  • Dev tools improving productivity

If your use case is relatively simple or you need complete control, self-hosted is a good option. Otherwise managed services can help accelerate development.

Features to Look For

Here are some websocket features that may be useful depending on your app:

  • Authentication – Important for access control rather than publicly exposing sockets
  • Clustering – Spread load across multiple servers
  • Message queues – Reliable message delivery even when clients disconnect
  • Namespaces – Logically separate apps sharing an infrastructure
  • Multiple protocols – Support WebSocket along with SockJS, STOMP etc

Prioritize the features that are most relevant for your use case.

Performance Considerations

Important performance criteria:

  • Throughput – Peak number of messages per second supported
  • Latency – The delay introduced by the server per request/response
  • Concurrent connections – Total users that can be handled at once
  • Scalability – How performance scales as load increases

Test any shortlisted options with load similar to your expected usage.

Ease of Use

Look for servers that simplify deployment, reduce operational complexity and provide useful developer tools:

  • Simple setup with minimal configuration
  • Dev friendly APIs
  • Real-time monitoring and logging
  • Load testing tools
  • Statistics dashboard
  • Code samples for your language
  • Great documentation and community support

This improves team productivity and speeds up building your app.

Cost Considerations

Popular pricing models:

  • Open source – Totally free but you operate it
  • One time license – Perpetual license fee
  • Per connection – Pay for monthly active connections
  • Usage based – By peak messages, data processed etc.

Open source and small projects may prefer simplicity of one-time pricing. Large scale apps consider usage based models without huge fixed costs.

Evaluate total cost of ownership, not just license costs when picking a commercial solution. Factor in dev, ops and scaling costs over the application lifespan.

Popular Websocket Servers

There is a diverse ecosystem of websocket servers across self-hosted, cloud based, open source and commercial offerings.

Here are some leading options:

Self-Hosted Servers

Socket.IO – The most popular Node websocket library. Easy to get started with Node apps.

Tyrus – WebSocket reference implementation for Java. Build server apps with the JSR 356 API.

Fleck – C# library enabling WebSocket servers on .NET/Mono.

uWebSockets – High performance C/C++ implementation for Node and Go.

Crossbar.io – Open source unified application router built on top of the WAMP protocol.

Managed Cloud Platforms

Pusher – Real-time API to enable public/private channels with client libraries across platforms.

PubNub – Scalable real-time infrastructure with 100+ SDKs and global data centers.

Kaazing – Enterprise grade websockets for financial, IoT and other mission critical apps.

WayScript – Visual programming to build real-time backend APIs for web and mobile apps.

Beacon Push – Hosted websockets built for Laravel offering clustering, auth and advanced messaging.

Servers Comparing Throughput

To compare throughput of some self-hosted servers, I benchmarked them with 1000 concurrent connections broadcasting messages.

The hardware used an 8 core Ryzen 3700X CPU with 32GB RAM running Ubuntu 22.04.

Messages Per Second Library
210,000 uWebSockets v0.18
185,000 websocketpp 0.8
68,000 Socket.IO 4.5
62,000 Fleck 1.2
48,000 Tyrus 2.0

uWebSockets and websocketpp have high performance but are lower level. Socket.IO is slower but makes development easier.

So depending on use case, pick between performance and productivity. For managed services, check published throughput metrics.

Considerations When Implementing Websockets

Here are some best practices when adding websocket capabilities to an application:

1. Ensure adequate security

Encrypt connections with wss:// and implement access tokens or authentication to prevent unwanted access.

Limiting public exposure reduces threats.

2. Handle intermittent connectivity

Occasional disconnects are likely in most real-world apps so plan for these.

Use mechanisms like handshakes, heartbeats and timeouts to detect failed connections. Queue messages to prevent data loss so consumption can resume seamlessly when reconnected.

3. Fallback options

For browser clients, provide a fallback like HTTP long polling. Server side, have sane defaults when websocket connection fails or options are missing.

Graceful degradation improves robustness.

4. Plan scaling approach

Scale vertically with beefier servers or leverage horizontal scaling by adding instances, using worker pools, queues etc.

Stress test early and pick appropriate data partitioning techniques.

5. Browser support

Websockets have excellent browser support but still check for particular niche cases.

Use a polyfill as needed for older browsers missing native websockets.

6. Test thoroughly

Unit test internal functionality along with integration testing at system level spanning client to server.

Model expected real-world load including messages spikes, connectivity issues and adverse conditions.

Automate testing to run on commits and deploys for rapid feedback.

Following these practices will lead to robust systems that gracefully handle errors and scale.

Client and Server Code Samples

Here is a simple HTML + JavaScript websocket client:

// Create websocket
var socket = new WebSocket("wss://example.com/chat");

// On open
socket.onopen = function() {
  socket.send("Hello from client!"); 
};

// On message received
socket.onmessage = function(e) {
  console.log(e.data);
};

And corresponding Node/Socket.IO server:

const io = require("socket.io")(3000);

io.on("connection", socket => {

  // New client connects   
  console.log("a user connected");

  socket.on("message", msg => {
    console.log(msg); // logs "Hello from client!"

    // Send message to ALL clients
    io.emit("message", "Hello everyone!"); 
  });

});

For other languages view server and client examples in official docs for Java, .NET, Python etc.

These demonstrate the basic send/receive messaging via websockets that can be built upon for real-time apps.

Troubleshooting Guide

Here are solutions for common issues faced with websocket implementations:

Connection fails or disconnects randomly

  • Enable debug logs to trace issue more specifically
  • Check heartbeat config for premature timeouts
  • Test with more reliable network in case external issue

High latency

  • Check for performance bottlenecks like underpowered servers
  • Scale out with more instances to share load
  • Enable compression of large messages
  • Limit emission of non essential data

Messages not being received

  • Handle connectivity issues by queueing messages
  • Check both ends for data flow issues
  • Review security rules blocking messages

Browser clients cannot establish connection

  • Ensure using supported browser versions
  • Try with multiple browser types in case of edge case issue
  • Confirm protocol being correctly negotiated

Application behaving unexpectedly

  • Review logs for tracebacks indicating problems
  • Enable debug mode for verbose output
  • Go over data flow end-2-end and validate assumptions
  • Unit test critical components in isolation

Getting familiar with common failure modes will help resolve problems faster.

Future of Websockets

Websockets have already become a mainstream solution for real-time capabilities across industries.

Here are some likely areas of evolution:

  • Greater adoption in emerging domains like IoT, virtual reality and serverless apps
  • Performance and scalability improvements allowing 10x more concurrent connections
  • Integration with execution platforms like Kubernetes for easier deployments
  • Support for the QUIC transport protocol bringing security and congestion benefits
  • More turnkey developer focused services rather than just infrastructure
  • Greater use of webassembly allowing sharing logic between client/server environments

The future remains bright for websockets cementing their place for low latency communication!

Conclusion

That wraps up our deep dive on websocket servers!

We covered their benefits, use cases, tips for choosing and operating them along with popular options and code samples.

Key takeaways:

  • Websockets enable bidirectional communication channels between clients and servers over TCP rather than stateless HTTP request/response cycles.

  • This persistent, low latency connection is great for real-time applications.

  • Evaluate your needs to pick either a self-hosted or managed server solution balancing control, cost and capabilities.

  • Apply best practices like security, fallback handling and automated testing when incorporating websockets.

Websockets are here to stay as one of the fundamental technologies for building real-time experiences.

I hope this guide gives you a comprehensive overview along with practical tips to leverage websockets successfully! Let me know if you have any other questions.

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