Libwebsockets

Libwebsockets is a simple-to-use, MIT-license, pure C library providing client and server for http/1, http/2, http/3, websockets, webtransport, MQTT and other protocols in a security-minded, lightweight, configurable, scalable and flexible way. It's easy to build and cross-build via cmake and is suitable for tasks from embedded RTOS through mass cloud serving.

It supports a lot of lightweight ancilliary implementations for things like JSON, CBOR, JOSE, COSE, and supports OpenSSL and MbedTLS v2/3/4 out of the box for everything. It's very gregarious when it comes to event loop sharing, supporting libuv, libevent, libev, sdevent, glib and uloop, as well as custom event libs.

100+ independent minimal examples for various scenarios, CC0-licensed (public domain) for cut-and-paste, allow you to get started quickly.

There are a lot of READMEs on a variety of topics. Doxygen API docs

We do a huge amount of CI testing per push

V5.0 now available... please upgrade to this or preferably v5.0-stable or main, as there are many security fixes only available on v5.0-stable and main; pre-5.0 releases are effectively deprecated.

• There's a continuous incremental security audit in place finding and fixing new problems all the time at the moment, it's not a sign the code is weak: it's a sign I am using frontier models to make it extremely strong.

• Code is pushed to main-dev now, Sai runs on it, if it passes, it is auto-promoted to main. Therefore from now on main only contains sai-tested pushes.

** NEW features available on v5.0 **

• Support for SChannel (windows native TLS, no need for OpenSSL build!), GnuTLS, openHiTLS and BearSSL added
• QUIC + H3 + Webtransport implementation, using aws-lc, wolfssl, boringssl, libressl, gnutls, and schannel (OpenSSL is h1/h2 -only; mbedtls can do it via a patch)
• WebRTC mixing (like your own zoom)
• HLS serving

LWS version	Platform	Protocols	Default TLS
<= 4.5	non-FreeRTOS	any	OpenSSL
<= 4.5	FreeRTOS	any	mbedTLS
5.0+	Windows	any	schannel
5.0+	*nix	h1, h2	OpenSSL
5.0+	*nix	quic/h3	GnuTLS
5.0+	FreeRTOS	any	mbedTLS

quic/h3 is enabled for build by default... necessitating GnuTLS instead of OpenSSL to make quic/h3 work.

TLS Library	Server TLS	Client TLS	QUIC Transport (TLS 1.3)	WSS / HTTPS	MQTT over TLS	ALPN (HTTP/2)	DTLS (WebRTC)	Session Cache	JIT Trust	GenCrypto
GnuTLS	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes
OpenSSL	Yes	Yes	No*	Yes	Yes	Yes	Yes	Yes	Yes	Yes
LibreSSL	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes
AWS-LC	Yes	Yes

* Note: 1) Upstream OpenSSL does not provide the necessary QUIC TLS API (SSL_set_quic_method) to act as a cryptographic engine for LWS's QUIC transport. If you need QUIC/HTTP3 support, we recommend using BoringSSL or GnuTLS. * *Note: 2) openHiTLS does not provide the necessary QUIC TLS API *

• DHT support built-in: -DLWS_WITH_DHT=1