HTTP vs. WebSocket

The foundation of the entire digital world is communication between machines. Authorized clients create a request, which the server receives, interprets, and provides an appropriate response. This is the common understanding of digital communication for ordinary people. However, the behind-the-scenes work is complex and tedious.

Application developers need to do a lot of work to ensure that this client-server communication functions properly. Choosing the right communication protocol is one of these tasks. When developers try to select a viable communication protocol, HTTP and WebSocket are two common concepts they will encounter.

Clarifying these two, their similarities, functions, and other aspects is crucial for ensuring the correct option is chosen based on actual needs.

Introducing HTTP#

Let's first understand HTTP. It is probably the most commonly used protocol in the field of digital communication. The initial version of HTTP was released in 1989, with limited functionality and application scope. But it was quickly improved and upgraded to support large-scale communication between browsers and servers.

HTTP is a one-way protocol, meaning that at any given time, only one party in the communication can send or receive information. When a client sends a request to a server, this request is sent in the form of HTTP or HTTPS, and the server sends a corresponding, unique response to the client after receiving the request. Each HTTP or HTTPS request establishes a new connection with the server and automatically terminates the connection after receiving the response.

Some main features of HTTP include:

• Stateless
• Can work based on connection-oriented protocols (such as SCTP and TCP)
• Information is encoded in ASCII
• The main components of an HTTP request include HTTP version (HTTP/1.1, HTTP/2, HTTP/3), method, HTTP header, host information, and message

What is WebSocket?#

WebSocket is a communication protocol that can achieve real-time two-way communication between client and server.

WebSocket is a protocol for creating real-time two-way communication channels in web applications. Unlike traditional HTTP requests (typically one request corresponds to one response), WebSocket can establish persistent connections, allowing the server to push data to the client in real-time while also receiving data from the client. Compared to traditional polling, WebSocket significantly reduces network traffic and latency, improving the efficiency and speed of data transmission. It is particularly suitable for developing real-time web applications and online games.

Some main features of WebSocket include:

• Based on persistent TCP connections, which remain open until the client or server initiates a termination request
• Built on the HTTP protocol, all WebSocket requests are sent through the standard HTTP protocol and then identified as specific header information Upgrade on the server side
• The WebSocket protocol is based on frames (data packets), a complete data packet can be divided into multiple frames, each frame containing a part of the data and header information

The relationship between HTTP and WebSocket#

From the above introduction, we can see that both HTTP and WebSocket protocols:

• Use TCP protocol for data transmission
• Are used for communication between client and server

We can more intuitively show the differences between HTTP and WebSocket through the following table.

HTTP	WebSocket
Establishes a new connection for each request (unless using HTTP long connections, such as HTTP/1.1 Keep-Alive), and closes the connection after communication ends	The connection remains open after successful initial handshake unless actively closed or an error occurs
One-way communication mode, client sends request, server returns response, each new communication requires re-establishing the connection	Two-way communication mode, after establishing the connection, client and server can send data at any time without re-establishing the connection
Each communication requires sending complete request and response headers, thus overhead is large for frequent short message communications	Once the connection is established, data transmission is lighter, no need to transmit header information each time, suitable for high-frequency, low-latency communication needs
Mainly used for transmitting relatively stable data	Mainly used for transmitting real-time data
Due to the need to re-establish connections for each request and carry necessary information through headers, etc., bandwidth usage efficiency and response speed are affected	Continuous connection eliminates the steps of establishing connections and necessary information for each request, resulting in lower latency and higher bandwidth usage efficiency
Frequent requests affect performance	Frequent requests do not affect performance

How to choose which protocol to use?#

Based on the comparison of advantages and disadvantages of HTTP and WebSocket in the previous section, we can evaluate usage scenarios from two different dimensions:

1. Whether the data changes rapidly, and whether the business depends on real-time data
2. Whether frequent two-way communication is involved

For example, if Jack wants to build a video chat application where each user needs to receive real-time video data from the chat partner and transmit their own video stream data to the other party, then WebSocket is the best choice.

Logto's Admin Console doesn't need to frequently obtain the current logged-in user's resource usage, because resources only change state when users modify configurations. It only needs to re-acquire the resource status in a timely manner when users operate on resources. From this perspective, HTTP is very suitable for Logto Admin Console's usage scenario. Similarly, for most cloud service dashboards, HTTP can be chosen as the communication protocol between the dashboard and server.