PubNub and Socket.IO are two separate technologies developers can use to power realtime messaging in web and mobile apps for use cases like live chat, multiplayer collaboration, and data broadcast. But which one should you use? In this article, we’ll look at how Socket.IO and PubNub compare. The following points are covered:
What is Socket.IO?
Socket.IO is an open-source realtime library that enables low-latency, bi-directional communication between web clients and servers. Built on top of the WebSocket protocol, Socket.IO provides additional capabilities compared to raw WebSockets:
Fallback to HTTP long polling for environments where WebSockets aren’t supported (e.g., older browsers and some corporate networks with proxy servers).
Disconnection detection, packet buffering, and automatic reconnections.
Broadcasting to all clients, or a subset of clients via rooms.
Acknowledgments (via callbacks).
Socket.IO advantages and disadvantages
Making use of namespaces enables you to minimize the number of TCP connections used, and save socket ports on the server, while broadcasting allows you to efficiently distribute data in scenarios where you need to fan out the same message to multiple users.
Socket.IO is easy to get started with; 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 must 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.
Socket.IO does not guarantee exactly-once messaging semantics. By default, Socket.IO provides an at-most-once delivery guarantee. This means there’s a chance some messages might never get delivered to recipients, especially when poor network conditions and disconnections are involved. If you’re unhappy with the default semantics, you can configure Socket.IO to provide an at-least-once messaging guarantee. However, this brings additional engineering complexity - you have to use acknowledgments, timeouts, assign a unique ID to each event, persist events in a database, and resend events upon reconnections.
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?
What is PubNub?
Serverless functions (PubNub Functions).
Authentication and encryption.
Fully-managed edge messaging infrastructure.
PubNub advantages and disadvantages
99.999% uptime SLA (for customers with the Pro package), and compliance with GDPR, SOC 2, CCPA, and HIPAA (the latter is only available for Pro customers).
Provides globally-distributed infrastructure spanning 15 datacenters, with data replication in multiple regions to protect against single points of failure.
PubNub does not guarantee that messages reach subscribers in the exact same order in which they are published. Message delivery is not guaranteed either - there’s a queue limit of 100 messages. If more than 100 messages are published while a user temporarily loses connectivity (e.g., driving through a tunnel), older messages will get discarded, and will never be delivered to the user once they reconnect.
HTTP long polling is used for realtime communication between PubNub servers and clients. Note that long polling is an inferior option to other realtime transports. For example, compared to WebSockets, long polling is more resource-intensive, and has higher latencies.
PubNub has a rather complex pricing model. It’s based on the number of monthly active users (MAUs), plus the number of transactions per month. However, there are tens of different transaction types, making it difficult to calculate and predict ongoing costs. Exceeding the number of MAUs & transactions allowed for your package may result in automatically being upgraded to a more expensive plan, or having your product keys locked.
Comparing PubNub and Socket.IO
We’ll now look at the high-level similarities and differences between PubNub and Socket.IO, compare their features, and briefly cover their use cases.
How are PubNub and Socket.IO similar?
The most obvious similarity is that PubNub and Socket.IO are technologies you can use to power realtime functionality in web and mobile apps.
Another similarity is that both PubNub and Socket.IO offer some flexibility in terms of messaging patterns. To be more exact, PubNub and Socket.IO can be used for 1:1 messaging, but also for 1:many communication. This is made possible by PubNub Channels (pub/sub channels), respectively Socket.IO’s broadcast and rooms features.
PubNub and Socket.IO use cases
PubNub and Socket.IO can both be used to power realtime network communication for several different types of use cases:
Live chat. 1-to-1 and group chat, chat bots, in-app chat.
Data broadcast. High-frequency updates sent in a 1-to-many fashion, such as live scores and traffic updates, live captions, voting, polling, and auction apps.
Multiplayer collaboration. Multiplayer games, whiteboards, and co-authoring apps (such as Google Docs).
GPS location tracking for urban mobility and food delivery apps.
How are PubNub and Socket.IO different?
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, PubNub is a commercial (paid) solution.
Another key difference - with Socket.IO, you have to host and manage your own server cluster (or find someone to do it for you). In comparison, PubNub is a managed, globally-distributed, cloud-based offering. It's arguably easier and less time-consuming (from an engineering point of view) to use a PubNub setup than it is to configure and manage your own cluster of Socket.IO servers.
A major difference is that Socket.IO primarily uses WebSockets (with HTTP long polling as a fallback) for realtime communication. In comparison, PubNub uses long polling, a WebSocket precursor. See how WebSockets compare to long polling.
PubNub offers more capabilities compared to Socket.IO. For example, it provides push notifications, webhooks, serverless functions, and presence, which are missing from Socket.IO’s feature set.
The last difference we’re going to mention is security. Socket.IO provides limited native security capabilities; for example, there’s no out-of-the-box mechanism to generate and renew tokens for authentication. In comparison, PubNub has better native security capabilities, such as TLS and AES-256 encryption, authentication (secret keys and tokens), and compliance with GDPR, SOC 2, CCPA, and HIPAA.
PubNub vs. Socket.IO: Features and capabilities compared
The table below compares PubNub and Socket.IO features and capabilities. (Note that the table is scrollable).
Hosted/managed for you.
You have to self-host / manage it yourself.
Claims it can handle unlimited concurrent connections and unlimited channels.
PubNub advertises sub-250ms worldwide latencies.
PubNub has a globally-available mesh architecture with no central point of failure.
Socket.IO is designed to work in a single region.
99.999% uptime SLA for customers with the Pro package.
Unclear if any SLA is provided for the Starter and Free tiers.
Guaranteed message ordering
PubNub does not guarantee message order and in general does not guarantee that messages are stored or sent in the exact same order in which they are published.
Yes (according to the documentation).
PubNub is not a guaranteed message delivery service.
Reconnections with continuity
PubNub SDKs support automatic reconnections.
However, there’s a queue limit of 100 messages. If more than 100 messages are published while a user is disconnected, older messages will get discarded, and will never be delivered to the user once they reconnect.
Provides automatic reconnections, but some messages may never get delivered upon reconnection.
HTTP long polling
WebSockets (primary) and HTTP long polling (fallback)
PubNub makes it possible to capture, filter, send and receive custom events and actions.
Socket.IO allows you to emit events in different ways, including:
Note that there are some reserved events names that you shouldn’t use in your app. Examples include:
PubNub offers integrations with tools such as:
- Agora and Vonage (for voice and video calls).
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.
Yes (PubNub Functions)
Yes (PubNub channels)
TLS and AES-256 encryption, secret API keys and tokens for authentication, compliance with GDPR, SOC 2, CCPA, HIPAA (the latter is only available for Pro customers).
Limited native security capabilities (e.g. CORS support). Doesn’t provide more complex features like a mechanism to generate and renew tokens, or end-to-end encryption.
The PubNub pricing model is based on:
It’s difficult to calculate and predict ongoing costs. Exceeding the number of MAUs & transactions allowed for your package may result in automatically being upgraded to a more expensive plan, or having your product keys locked.
Note that PubNub also charges for support.
PubNub and Socket.IO alternatives
We hope this article is a good starting point for you to discover the advantages, disadvantages, similarities, and differences between PubNub 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 powered by Socket.IO is a complicated affair. For more details about the challenges and complexities of building scalable realtime experiences with Socket.IO, check out Scaling Socket.IO - practical considerations.
Although PubNub removes the need to manage realtime infrastructure yourself, it comes with its own limitations. For example, it uses HTTP long polling as the transport protocol for realtime communication, which is inferior in almost every way compared to WebSockets. Furthermore, PubNub provides rather weak assurances regarding data integrity (message ordering and delivery are not guaranteed).
It is ultimately up to you to decide if PubNub/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:
Ably, the most reliable and scalable alternative to PubNub and Socket.IO
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.
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 (P99).
Elastic scalability to handle up to millions of concurrent clients, and a constantly fluctuating number of connections and channels.
Find out more about Ably and how we can help with your realtime use case:
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