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  6. Pusher vs. Socket.IO: differences, similarities, and feature comparison
7 min readPublished Jan 19, 2023

Pusher vs. Socket.IO: differences, similarities, and feature comparison

This blog post compares Pusher and Socket.IO, two event-driven technologies developers can use for realtime use cases like live chat, broadcasting high-frequency updates (e.g., live sports scores), or realtime location tracking. We’ll cover the following:

Copy link to clipboardWhat is Pusher?

Acquired by MessageBird in 2020, Pusher is a cloud service designed to add realtime data and functionality to web and mobile applications. It provides hosted APIs and managed messaging infrastructure. There are two Pusher products:

  • Pusher Channels - pub/sub channels over WebSockets, with features like automatic fallbacks, authentication and authorization, and a queryable API. 

  • Pusher Beams - an API for cross-platform push notifications for iOS, Android, and Web.

Copy link to clipboardPusher advantages and disadvantages

We’ll now cover some of Pusher’s main advantages and disadvantages.

Copy link to clipboardPusher pros

  • Pusher primarily uses WebSockets, but will also fall back to HTTP in environments where WebSockets aren’t supported. 

  • SDKs for every major development platform and programming language, giving you the flexibility of integrating Pusher in your preferred language.

  • Features such as presence (useful, for example, for chat apps), webhooks to capture and respond to client events as they happen, and end-to-end encryption for enhanced security.

Copy link to clipboardPusher cons

  • No superior QoS messaging guarantees; for example, if a message is published whilst a client is briefly disconnected (such as going through a tunnel or changing networks), then the message published over Pusher will never arrive to that client.

  • Pusher does not provide integrations with services such as event streaming platforms (e.g., Kafka) and serverless platforms (e.g., AWS Lambda, Azure Functions, etc.). Note that these are often used as part of a wider realtime ecosystem.

  • Pusher requires you to choose a single datacenter for an app to reside in. All realtime traffic must therefore be routed through that single datacenter, regardless of a user’s location. This has implications for performance, reliability, and availability.

Copy link to clipboardWhat is Socket.IO?

Socket.IO is an open-source realtime 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 compared to raw WebSockets:

  • Fallback to HTTP long-polling for environments where WebSockets aren’t supported (e.g., some older browsers and corporate networks with proxy servers)

  • Disconnection detection, packet buffering, and automatic reconnections.

  • Multiplexing (namespaces).

  • Broadcasting to all clients, or to a subset of clients via rooms.

  • Acknowledgments (via callbacks).

Copy link to clipboardSocket.IO advantages and disadvantages

We’ll now cover some of Socket.IO’s key advantages and disadvantages.

Copy link to clipboardSocket.IO pros

  • Making use of namespaces enables you to minimize the number of TCP connections used, and save socket ports on the server, while broadcasting enables you to more efficiently distribute data to clients. 

  • Socket.IO is easy to use; it provides a simple API for both the client side and the server side, making it straightforward to implement realtime functionality into your application. 

  • Integrations with various solutions for horizontal scaling: Redis, MongoDB, Postgres, AMQP / RabbitMQ, so you can choose the one that best suits your needs. Note that you have to use one of these when you scale beyond a single Socket.IO server, to pass events between nodes, and ensure that events are properly routed to all clients.

Copy link to clipboardSocket.IO cons

  • Socket.IO does not guarantee exactly-once messaging semantics. By default, an at-most-once guarantee is provided. Socket.IO can also be configured to provide at-least-once guarantees, although this brings additional engineering complexity  - you have to use acknowledgments, timeouts, assign a unique ID to each event, and persist events in the database. 

  • Socket.IO comes with limited native security features. For example, it doesn't provide end-to-end encryption, and it doesn't offer a mechanism to generate and renew tokens for authentication.

  • Socket.IO is designed to work in a single region, rather than a multi-region architecture. This can lead to issues such as increased latency (if your users are in different regions), and even system downtime - what happens if the datacenter where you have your Socket.IO servers goes through an outage?

Learn more about Socket.IO’s pros and cons

Copy link to clipboardComparing Pusher and Socket.IO

We’ll now look at the high-level similarities and differences between Pusher and Socket.IO, compare their features, and briefly cover their use cases. 

Copy link to clipboardWhat are the similarities between Pusher and Socket.IO?

The most obvious similarity is that Pusher and Socket.IO are technologies you can use to power real time functionality in web and mobile apps. They both use the WebSocket protocol as the main underlying transport for sending and receiving data, while offering additional capabilities on top of raw WebSockets, such as automatic fallback to HTTP. See how Pusher and Socket.IO compare to WebSockets:

Another similarity is that Pusher and Socket.IO both offer some flexibility in terms of messaging patterns. To be more exact, SignalR and Socket.IO can be used for 1:1 messaging, but also for 1:many communication. This is made possible by Pusher Channels (pub/sub channels), respectively Socket.IO’s broadcast and rooms features. 

The final similarity we’ll bring up in this section: Pusher and Socket.IO are designed to work in a single region, rather than in a multi-region architecture. A single-region design can lead to issues such as:

  • Increased latency. If perhaps you’re building a game or financial services platform, and latency matters to you, then you have a problem if your visitors are not near your servers. If, for example, you have two users playing a realtime game in Australia, yet your Socket.IO / Pusher servers are located in Europe, every message published will need to go halfway around the world and back.

  • System downtime. What happens if the region where you have your Socket.IO / Pusher servers is unavailable? Your system would experience downtime, and could become unavailable to your user base (unless you have a backup deployment, which adds engineering complexity and costs). 

Copy link to clipboardWhat kind of realtime features can you build with Pusher and Socket.IO?

Pusher and Socket.IO both address largely the same use cases. You can use them to build realtime apps and features such as:

Copy link to clipboardWhat are the key differences between Pusher and Socket.IO?

The first difference of note is that Socket.IO is an open-source technology; its source code is freely available for developers to use. In contrast, Pusher is a commercial (paid) solution. Another key difference is that you have to host and manage Socket.IO yourself (or find someone to do it for you). In comparison, Pusher is a managed, cloud-based offering.  

Pusher offers more capabilities compared to Socket.IO. For example, it provides push notifications, webhooks, and presence, which are missing from Socket.IO’s feature set. Pusher also has more client and server SDKs, for a considerable range of programming languages and platforms (Java, Android, iOS, JavaScript, Unity, React Native, Python, etc). Meanwhile, Socket.IO offers one official Socket.IO server implementation (Node.js), and four official client implementations (JavaScript, Java, C++, Swift). Note that there are also a few community-maintained server and client implementations in other languages, such as Python and Golang. 

The last difference we’re going to mention is security. Socket.IO provides limited native security capabilities, with no support for end-to-end encryption, and no out-of-the-box mechanism to generate and renew tokens for authentication. In comparison, Pusher has better native security capabilities, such as end-to-end encryption and baked-in authentication. 

Copy link to clipboardPusher vs Socket.IO: comparing features and capabilities

The following table compares Pusher and Socket.IO features and capabilities:

Feature/Capability

Pusher

Socket.IO

Pricing

Pusher prices its two products - Channels and Beams – separately and in tiers. The nature of realtime messaging and streaming data over the public internet means WebSocket connections, required channels, and messages often fluctuate. Plus it’s never easy to estimate how much you’ll need upfront anyway. With Pusher’s pricing model, if you exceed any one attribute of a tier you’ll likely be forced into another more expensive tier.

N/A

Infrastructure

Hosted / managed for you.

You have to self host / manage it yourself.

Scalability

Unclear to what extent Pusher can scale.

Unclear to what extent you can scale Socket.IO, but it’s a difficult challenge.

Latency

Claims to offer <240 ms latencies.

Unknown.

Is there a single point of failure?

Pusher apps are located in a single datacenter rather than distributed across multiple datacenters. If that datacenter goes offline then all apps hosted there are affected.

When you scale beyond one single Socket.IO / WebSocket server, you need to use a tool such as Redis to keep your servers in sync, and ensure that updates are delivered to all relevant clients. However, like all services, you have to expect maintenance windows and some unexpected downtime. When your Redis server (or whatever similar solution you plan to use) is down, your system will also be severely affected.

Uptime SLA

99.95% (this amounts to 4h 22m 58s downtime per year).

N/A

Single-region or multi-region?

Pusher requires you to choose a single datacenter for an app to reside in. All realtime traffic must therefore be routed through a single datacenter, regardless of a user’s location.

Socket.IO is designed to work in a single region.

Guaranteed message ordering

No

Yes (according to the documentation)

Guaranteed message delivery (exactly-once)

No

No

Reconnections with continuity

Provides automatic reconnections, but some messages may never get delivered upon reconnection.

Provides automatic reconnections, but some messages may never get delivered upon reconnection.

Native push notifications

Pusher provides push notifications through its “Beams” product.

No

Transport protocols

WebSockets

HTTP (fallback)

WebSockets

HTTP long polling

Webhooks

Yes

No

Integrations

No integrations with third-party services, serverless platforms (e.g. Azure Functions, AWS Lambda) or event streaming platforms (like Kafka or AWS Kinesis), which are often used in realtime architectures.

Only provides a few integrations with tools like Redis, MongoDB, and Postgres. You need to use one of them if you plan to scale to more than one Socket.IO server.

Serverless functions

No

No

Message history

No

No

Pub/sub messaging / broadcast

Pusher provides pub/sub messaging over WebSockets via its “Channels” product.

Socket.IO also allows the server to flexibly broadcast events to clients. You can broadcast to all connected clients, or use the rooms feature to broadcast events to a subset of clients (who have joined the room).

Message and worker queues

No

No

Presence

Yes

No

Security

Security features include authentication and authorization and end-to-end encryption. 

Pusher is not compliant with standards such as SOC 2 or HIPAA. 

Limited native security capabilities (e.g. CORS support). Doesn’t provide more complex features like a mechanism to generate and renew tokens, and end-to-end encryption.

SDKs

Pusher has client and server SDKs for a considerable range of programming languages and platforms (Java, Android, iOS, JavaScript, Unity, React Native, Python, etc).

Initially, Socket.IO provided a Node.js server and a JavaScript client implementation. More recently, several other server and client SDKs have appeared, targeting languages like Python, Go, and Java (most are community-made and might have a limited feature set).

Copy link to clipboardPusher and Socket.IO alternatives

We hope this article is a good starting point for you to discover the advantages, disadvantages, similarities, and differences between Pusher and Socket.IO.

Whilst Socket.IO is open-source, and its source code is freely available for any developer to use, building dependable realtime features for end users is a complicated affair. For more details about the challenges and complexities of building scalable realtime features with Socket.IO, check out Scaling Socket.IO - practical considerations

Although Pusher removes the need to manage realtime infrastructure yourself, it comes with its own limitations. For example, it requires you to choose a single datacenter for an app to reside in, which has negative implications on performance, reliability, and availability. Other similar realtime platforms, such as Ably, offer superior guarantees. See how Pusher compares to Ably

It is ultimately up to you to decide if Pusher / Socket.IO is the best choice for your specific realtime use case. However, if you’re interested in further weighing your options, here are some alternative solutions you can explore:


About Ably

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. 

Find out more about Ably and how we can help with your realtime use case:

Get started with a free Ably account and give our WebSocket APIs a try.

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