Pusher vs WebSockets: Pros, cons and key differences

WebSockets 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.

WebSockets includes two core building blocks:

• The WebSocket protocol. Standardized in December 2011 through RFC 6455, the WebSocket protocol enables realtime communication between a WebSocket client and a WebSocket server over the web. It supports the transmission of binary data and text strings.

• The WebSocket API. Allows you to perform necessary actions, like managing the WebSocket connection, sending and receiving messages, and listening for events triggered by a WebSocket server. All modern browsers support the WebSocket API.

WebSockets are free to develop an application with, but they don’t come with many features out of the box. Developing an app using raw WebSockets would mean having to write a lot of functionality yourself, whether you want pub/sub messaging, user presence, authentication, etc.

Pusher is a realtime application platform, which promises rapid, scalable, flexible application development. It offers SDKs for building client and server components, with support for various platforms across web, desktop, mobile, and IoT.

Pusher provides a free sandbox option for evaluation and development with up to 200K messages per day and 100 concurrent users. In return you get a managed infrastructure based on a pub/sub architecture, with key features including authentication, detecting user presence, reacting to events, fallbacks to HTTP for environments where WebSockets aren’t supported, and more. These features can save a lot of development time.

• 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.

• Flexibility is ingrained into the design of the WebSocket technology, which allows for the implementation of application-level protocols and extensions for additional functionality (such as pub/sub messaging).

• As an event-driven technology, WebSocket allows data to be transferred without the client requesting it. This characteristic is desirable in scenarios where the client needs to react quickly to an event (especially ones it cannot predict, such as a fraud alert).

• Free to use.

• WebSocket is stateful. This can be tricky to handle, especially at scale, because it requires the server layer to keep track of each individual WebSocket connection and maintain state information.

• WebSockets don’t automatically recover when connections are terminated – this is something you need to implement yourself, and is part of the reason why there are many WebSocket client-side libraries in existence.

• Certain environments (such as corporate networks with proxy servers) will block WebSocket connections, while some browsers still don't support WebSockets.

• Not many features provided out of the box.

• 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.

• Pusher is not free to use; it can become costly as you scale.

• Pusher has multiple datacenters available, but unlike other realtime platforms it 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. This has implications for performance, reliability, and availability.

• 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.).

We can broadly group WebSocket use cases into two main categories:

• Realtime updates, where the communication is unidirectional, and the server is streaming low-latency (and often frequent) updates to the client. Think of live sports updates, alerts, realtime dashboards, or live location tracking.

• Bidirectional communication, where both the client and the server send and receive messages. Examples include chat applications, virtual events, and virtual classrooms (the last two usually involve features like polls, quizzes, and Q&As). WebSockets can also be used to underpin multi-user synchronized collaboration functionality, such as multiple people editing the same document simultaneously.

Pusher is suited to a range of use cases, including:

• Chat apps

• Realtime polling, statistics, and graphs

• Location apps

• Live sports commentary

• Education/virtual classrooms

WebSockets are a low-level protocol that enables two-way realtime communication between client and server. In contrast, Pusher channels are a service that provides an abstraction layer on top of WebSockets, with many features provided by default to make it easier to create realtime applications.

WebSockets in essence are simpler and have lower memory requirements than Pusher. However, Pusher is a more complex and feature-rich solution than raw WebSockets.

Whether you should use Pusher or WebSockets depends on a couple of factors. Firstly, the specifics of your use case. Raw WebSockets are suitable for simplistic use cases, such as sending data to browsers. For more complex use cases, such as a chat app, Pusher Channels are a superior alternative, allowing you to build a feature-complete app faster than plain WebSockets.

Another aspect to bear in mind is the degree of flexibility you need for your use case. Raw WebSockets provide more flexibility — you can design your own architecture and your own protocol on top (although this is incredibly difficult and time-consuming). In contrast, Pusher comes with a pre-designed architecture and protocol, which may become restrictive at some point. In addition, it is a proprietary solution that could leave you feeling locked in, and will make it harder to migrate to and from another solution.

Irrespective of your choice, building dependable realtime functionality and delivering it at scale to end-users is far from trivial.

It's worth noting that Pusher and WebSockets are not the only technologies you can use to build realtime features. If you are interested in reading about alternatives, take a look at:

• WebSocket alternatives for realtime features

• Pusher alternatives

If you want to avoid the headache and high costs of managing WebSocket infrastructure in-house, Pusher might be a good option, or you might want to consider investigating other fully-managed WebSocket solutions such as Ably (see Ably vs Pusher for a full comparison).

Ably is a serverless WebSocket platform operating at the edge. We make it easy for developers to build live and collaborative experiences for millions of users in a few lines of code, without the hassle of managing and scaling WebSocket infrastructure. Our platform is underpinned by a globally-distributed, autoscaling edge network.

We provide robust capabilities and guarantees, including 25+ client SDKs targeting every major platform and programming language, feature-rich pub/sub APIs, and guaranteed message ordering and delivery.

To find out more about what Ably can do for you, get started with a free account.