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tatsuhiro-t/wslay

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The WebSocket library in C

FreeFree tier
Type
Open Source
Visit Website GitHub (38 stars)

About tatsuhiro-t/wslay

Wslay is a lightweight WebSocket library written in C, implementing protocol version 13 as defined in RFC 6455. It offers two API levels: an event-based API suited for non-blocking reactor patterns with user-defined callbacks, and a frame-based low-level API for direct WebSocket frame manipulation. The library supports text and binary messages, automatic ping replies, and integrates with external event loops. Wslay does not perform any I/O operations itself, relying on callback functions for all I/O, making it portable across platforms and independent of specific networking or SSL frameworks. It only handles the data transfer portion of the WebSocket protocol and does not perform the HTTP opening handshake. Licensed under MIT.

Key Features

Implements WebSocket protocol version 13 (RFC 6455)
Two API levels: event-based (callback-driven, non-blocking) and frame-based low-level
Supports text and binary messages
Automatic ping reply handling
Callback interface for flexible integration
External event loop support
No I/O operations – relies on callbacks for portability
MIT licensed open source

Pros & Cons

Pros
  • Lightweight and portable due to no built-in I/O dependencies
  • Flexible API design with two abstraction levels
  • Compliant with the standard WebSocket protocol (RFC 6455)
  • Clean callback-based architecture for non-blocking use
  • Free and open source (MIT license)
Cons
  • Does not perform the HTTP opening handshake (requires separate handling)
  • Only supports data transfer, not the full WebSocket lifecycle
  • Limited to C language use
  • No built-in SSL/TLS support (depends on external I/O code)

Best For

Building WebSocket servers or clients in CEmbedding WebSocket capabilities into existing event-driven applicationsDeveloping lightweight, portable networking tools that require WebSocket support

FAQ

Does wslay handle the WebSocket opening handshake?
No, wslay only supports the data transfer part of the WebSocket protocol. The HTTP opening handshake must be implemented separately by the application.
What API levels does wslay offer?
Wslay provides two API levels: an event-based API suitable for non-blocking reactor patterns with callbacks, and a frame-based low-level API for direct WebSocket frame construction and parsing.
Is wslay dependent on any specific I/O framework or SSL library?
No. Wslay does not perform any I/O operations itself; it uses callbacks for all I/O, making it independent of any I/O framework, socket library, or SSL implementation.