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Pros and Cons of WebSocket and EventSource by@michaelpautov

Pros and Cons of WebSocket and EventSource

Michael Pautov Hacker Noon profile picture

Michael Pautov

Software Engineer

What is Websocket?

Websockets are a sort of PUSH technology that allows bidirectional communication over a single (TCP) socket. It's a protocol that uses a single TCP socket to provide bidirectional, full-duplex communication channels. It was created with web browsers and servers in mind, but it can be used by any client or server program.

Messages between client and server are depicted in the diagram. Websockets use handshake messages to establish or open connections, whereas HTTP uses the request-response messaging mechanism. Websockets are full-duplex, while HTTP is half-duplex.

It's a protocol that allows programmers to create a permanent connection between a client and a server and send data in real-time. Messages can be transmitted between the TCP sockets of a single connection (simultaneously or back and forth).

What is the purpose of WebSocket?

The limitations of HTTP-based technology were the inspiration that brought about the development of WebSockets. A client will request a resource using HTTP, while the server will respond with the details. HTTP is a one-way protocol, which means that all data sent from the server to the client must be requested at first.

Long-polling has historically been used to get around this restriction. Long-polling is when a client sends an HTTP request with a long timeout, and the server uses the timeout to send data to the client. Long-polling works, but it has a drawback: it ties up server resources for the duration of the long poll, even though no data is available to submit.

WebSockets, in the other way round, allow the transmission of message-based data in a manner similar to UDP but with the security of TCP. WebSocket uses HTTP as the initial transport method but leaves the TCP link open after the HTTP response is received so that messages can be sent between client and server. WebSockets allow us to create “real-time” applications without requiring the use of long pollination.

Advantages of WebSocket 

  • It allows for two-way communication.
  • Websockets allow you to send and receive data much faster than HTTP. They're also faster than AJAX.
  • Communication between origins (however, this poses security risks).
  • Compatibility between platforms (web, desktop, mobile)
  • HTTP has a 2000-byte overhead, but WebSocket only has a 2-byte cost.
  • Long polling is replaced.
  • AJAX calls can only send string data types because WebSockets are data typed.

Cons of Websocket

  • A fully HTML5-compliant web browser is required.
  • AJAX-like success mechanisms are not available in Websockets.
  • Websockets, unlike HTTP, do not provide intermediary/edge caching.
  • It is impossible to employ friendly HTTP statuses, bodies, and other elements to create even a simple protocol of your own.
  • HTTP is significantly easier to develop if your application doesn’t take a lot of dynamic interaction.

Pros of EventSource:

  • It's ideal for fail-safe situations. If the downstream source fails, the event store can be used to reassemble the data.
  • Extremely adaptable Any message type can be saved. As long as suitable access credentials are allowed, any customer can access the event store.
  • When combined with an event-driven message broker like Kafka, it's ideal for real-time data reporting.
  • Entity instances are typically represented as both a mutable object in memory and a modifiable row in a relational database table in the classic CRUD style—the famed object-relational impedance mismatch results as a result of this. Object-relational mappers were built to bridge this gap, but they come with their own set of complications. The database is treated as an append-only log of serialized events in the event source architecture. It doesn't try to directly model each entity’s state or their relationships in the database schema. The code for writing to and reading from the database is substantially simplified as a result of this.
  • The stored events contain the history of how an entity came to be in its current state. Because transactional and audit data are the same, there is no need to worry about inconsistency.
  • You may now evaluate the event stream and extract valuable business information – possibly information that was not considered when the events were planned. You can expand your system's activity by adding new views without complicating the write-side.
  • Because all events are simply appended to the data storage, it increases write performance. No changes have been made, and no deletions have been made.
  • Event-driven systems are simple to test and troubleshoot. For testing reasons, commands and events can be emulated. The event log is a useful tool for debugging. If a problem is discovered in production, you can use a controlled environment to replay the event log to figure out how an object got into a problematic condition.

Cons of EventSource:

  • Given the pattern's intrinsic temporal sensitivity and susceptibility to potential latency concerns, it requires an exceedingly efficient network infrastructure.
  • Requires a dependable method of controlling message formats, such as a schema registry.
  • Payloads will differ depending on the event. For defining and establishing message formats for a certain event, there should be a single source of truth.


The classification of WebSockets as the model for data push and real-time communication is somewhat of a misnomer around the web as it is described nowadays. Independent of some open-source resolutions, WebSockets are just a part of the puzzle when developing real-time applications.

There is a slew of operational issues a developer may run into when using WebSockets as their real-time solution, particularly as the app scales and the user base grows technology like: Firewalls, Network topology, Load testing, and Security.