Open Source C# WebSocket Servers

Fleck is a lightweight WebSocket server implementation for C# applications. It gives developers a simple way to accept WebSocket connections without requiring inheritance-heavy frameworks, containers, or extra server dependencies. The project is designed to be easy to embed inside desktop apps, services, prototypes, tools, and custom .NET servers. Fleck exposes straightforward callbacks for connection open, close, message, binary, ping, and pong events. It does not depend on HttpListener or HTTP.sys, which makes it usable in environments where those Windows components are not appropriate. It is best suited for developers who need a small, direct WebSocket server layer rather than a full web framework.

SuperSocket is a high-performance, extensible socket server framework for .NET applications. It provides a structured foundation for building custom network communication servers without manually implementing every low-level socket concern. The framework supports multiple protocols, including TCP, UDP, and WebSocket, and gives developers a modular architecture for protocol parsing, session handling, command processing, and server hosting. It is suitable for chat servers, game servers, IoT gateways, telemetry services, industrial systems, and other real-time network applications. SuperSocket is designed to be flexible enough for custom binary or text protocols while still offering reusable abstractions for common server patterns. It is most useful for .NET teams that need robust networking infrastructure with room for domain-specific protocol logic.

Implementation of the WebSocket protocol, along with client and server integration components.

High-performance dotnet core socket tcp communication components, support TLS, HTTP, HTTPS, WebSocket, RPC, Redis protocols, custom protocols and 1M connections problem solution.

Ultra fast and low latency asynchronous socket server & client C# .NET Core library with support TCP, SSL, UDP, Unix Domain Socket, HTTP, HTTPS, WebSocket protocols and 10K connections problem solution. Has an integration with high-level message protocol based on Fast Binary Encoding. Cross-platform (Linux, MacOS, Windows) Asynchronous communication. Supported transport protocols: TCP, SSL, UDP, UDP multicast, Unix Domain Socket. Supported Web protocols: HTTP, HTTPS, WebSocket, WebSocket secure. Supported Swagger OpenAPI iterative documentation. Supported message protocol based on Fast Binary Encoding.

This library is a WebSocket server/client library with HTTP server capability. Sample chat server/client apps attached. * .NET 4.5 required * WPF application

WebSocket RPC library for .NET with auto JavaScript client code generation, supporting ASP.NET Core.

The WebSocketListener class provides simple methods that listen for and accept incoming WebSocket connection requests asynchronously. It is a lightweight listener with an API very similar to the System.Net.TcpListener class. It does not use the Microsoft's System.Net.WebSockets namespace. WebSocketListener has been designed to provide WebSocket connectivity to other applications, in the same way that System.Net.TcpListener provides TCP connectivity. It is not a communication framework on its own and it does not provide any kind of publisher/subscriber pattern or reliable messaging beyond TCP.

A simple, zero-dependency WebSocket server for Unity. The easiest way is to use the inspector. Add callbacks to the onOpen, onMessage, or onClose UnityEvent. Alternatively, you can inherit from WebSocketServer.