Eclipse Tyrus is the open source JSR 356 - Java API for WebSocket
Command-line client for WebSockets, like netcat (or curl)
Compliant web server for the most demanding of applications
Future-based Tungstenite for Tokio
Polyglot replacement for Ruby WebSocket servers with Action Cable
Minimalist websocket framework for Go
Ultra fast and low latency asynchronous socket server & client C#
golang supports million-connection distributed chat (IM) system
WebSockets in C for Embedded Applications
Socket.io implementation for Vuejs and Vuex
Python binding to the libindi library
REST and websockets C++ library
Implementation of the WebSocket protocol, along with client and server
Karellen Gevent Websocket Library