What is Socket.IO?
Created back in 2010, Socket.IO is a well-known open-source library that enables low-latency, bi-directional communication between web clients and servers. Socket.IO is built on top of the WebSocket protocol and provides additional capabilities such as automatic reconnections, or falling back to HTTP long polling.
Socket.IO is used for developing realtime features such as:
5 alternatives to Socket.IO
We’ll now look at alternatives to Socket.IO - similar technologies that allow you to build realtime functionality for end-users. Here are the five alternatives we’ll cover:
DIY WebSocket solution
The Ably serverless WebSocket platform
DIY WebSocket solution
WebSocket is a realtime technology that enables bi-directional, full-duplex communication between client and server over a persistent, single-socket connection.
A WebSocket connection starts as an HTTP request/response handshake. If this initial handshake is successful, the client and server have agreed to use the existing TCP connection that was established for the HTTP request as a WebSocket connection. This connection is kept alive for as long as needed (in theory, it can last forever), allowing the server and the client to independently send data at will.
DIY WebSocket solution pros
WebSocket is a mature, widely-used technology; it emerged over a decade ago and has been extensively battle-tested. Most programming languages, development platforms, and browsers support WebSockets.
The WebSocket technology allows for the implementation of application-level protocols (on top of WebSockets), and extensions for additional functionality (such as pub/sub messaging). Building on raw WebSockets means you have the flexibility of designing your own WebSocket-based protocol and capabilities, tailor-made for your specific use case and needs.
Before WebSocket, HTTP techniques like AJAX long polling and Comet were the standard for building realtime apps. Compared to HTTP, WebSocket eliminates the need for a new connection with every request, drastically reducing the size of each message (no HTTP headers). This helps save bandwidth, improves latency, and makes WebSockets less taxing on the server side compared to HTTP.
DIY WebSocket solution cons
Certain environments (such as corporate networks with proxy servers) will block WebSocket connections. You will most likely have to consider supporting fallback transports for these scenarios.
Unlike HTTP, WebSocket is stateful. This can be tricky to handle, because it requires the server layer to keep track of each individual WebSocket connection and maintain state information.
Building a reliable DIY WebSocket solution that you can trust to deliver at scale is expensive, time-consuming, and requires significant engineering effort.
Here are some key stats to give you a taste of how complex it is to engineer WebSocket capabilities in-house:
65% of DIY WebSocket solutions had an outage or significant downtime in the last 12-18 months.
10.2 person-months is the average time to build basic WebSocket infrastructure, with limited scalability, in-house.
Half of all self-built WebSocket solutions require $100K-$200K a year in upkeep.
While its main transport is WebSocket, SockJS supports numerous fallback options, including Server-Sent Events, long polling, and JSONP-polling.
Intuitive, easy-to-use API, which makes getting started with SockJS quick and easy.
Active efforts are being made so that SockJS is available in additional programming languages, like Ruby, Java, Scala, Python, Erlang, and Rust.
SockJS is a simplistic WebSocket implementation, lacking features such as presence, automatic reconnections, pub/sub messaging, and message history. Additionally, it doesn’t guarantee data integrity (guaranteed delivery and ordering).
Evidence suggests SockJS doesn’t scale beyond 7000 concurrent users, which indicates that it’s more suitable for small and medium-scale projects rather than large-scale applications.
You can't open more than one SockJS connection to a single domain at a time.
Ably is a realtime experience infrastructure provider. Our realtime APIs and SDKs help developers power multiplayer collaboration, chat, data synchronization, data broadcast, notifications, and realtime location tracking at internet scale, without having to worry about managing and scaling messy realtime infrastructure.
Key Ably features and capabilities
Ably is underpinned by a globally-distributed network of datacenters and edge acceleration points of presence.
Client SDKs for every major programming language and development platform.
Pub/sub APIs with rich features, such as message delta compression, multi-protocol support (WebSockets, MQTT, Server-Sent Events), automatic reconnections with continuity, presence, and message history.
Guaranteed message ordering and delivery.
Global fault tolerance and a 99.999% uptime SLA.
< 65ms round-trip latency for 99th percentile.
Elastic scalability to handle millions of concurrent clients.
Here are some more resources for further reading:
Learn more about the Ably platform (features and system properties).
Explore customer stories and find out how organizations like HubSpot, Mentimeter, and Genius Sports benefit from trusting Aby with their realtime needs.
Sign up for a free account and see what Ably can do for you.
Rails ActionCable pros
Allows you to mount the WebSocket endpoint directly inside your app, which simplifies deployment significantly and allows sharing of cookies.
The ActionCable client-side library is responsible for maintaining a connection and reattaching all subscriptions to Channels. If, for example, your connection is abruptly terminated, the ActionCable client-side library will automatically reestablish a connection and subscribe to all previous subscriptions.
ActionCable is bi-directional so browser clients can receive data broadcasted using the
receivedmethod, but also send data to public methods using the client-side
Rails ActionCable cons
There is no acknowledgment of success or failure (ACK / NACK) for the publishing of messages from a client to the server. This can lead to some messages never being delivered (at-most-once semantics), and negatively impact the user experience. Additionally, message ordering is not guaranteed (no serial number/timestamp is attached to messages).
If you need to support devices or environments where WebSockets are blocked (e.g., corporate networks with proxy servers), the ActionCable is not a suitable option, as it doesn’t provide any fallback transports.
SignalR is a technology that enables you to add realtime web functionality to apps, primarily over WebSockets. SignalR comes in several different flavors:
ASP .NET SignalR - a library for ASP. NET developers. Note that this version is largely outdated (only critical bugs are being fixed, but no new features are being added).
ASP .NET Core SignalR - an open-source SignalR library; unlike ASP. NET SignalR, this version is actively maintained.
Azure SignalR Service - the fully managed cloud version.
SignalR uses WebSockets wherever possible, but it also supports two fallback transports: Server-Sent Events, and HTTP long polling, for environments where the WebSocket transport is blocked/unsupported.
Multiple backplane options to choose from when scaling out: Redis, SQL Server, or Azure Service Bus (note that there’s no need for a backplane when using the fully managed version, Azure SignalR Service).
Part of the ASP.NET Framework, which makes it easy to use SignalR in combination with other ASP.NET features like authentication, authorization, and dependency injection.
SignalR offers rather weak messaging QoS; ordering and delivery are not guaranteed. You’d have to come up with your own mechanism to ensure robust messaging (e.g., adding sequencing information to messages themselves).
SignalR is designed to be a single-region service, which can negatively impact its performance, reliability, and availability.
A brief conclusion
We hope you’ve found this article useful as a starting point for discovering Socket.IO alternatives. We encourage you to conduct an in-depth analysis and evaluation to see which one of the solutions we’ve covered is the best choice for your specific use-case.
If you’re looking for a scalable, feature-rich WebSocket service to build live experiences for end-users, and you don’t want to worry about managing complex infrastructure, we invite you to give Ably a go.
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