deniszykov.WebSocketListener 4.2.14

Install-Package deniszykov.WebSocketListener -Version 4.2.14
dotnet add package deniszykov.WebSocketListener --version 4.2.14
<PackageReference Include="deniszykov.WebSocketListener" Version="4.2.14" />
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add deniszykov.WebSocketListener --version 4.2.14
The NuGet Team does not provide support for this client. Please contact its maintainers for support.
#r "nuget: deniszykov.WebSocketListener, 4.2.14"
#r directive can be used in F# Interactive, C# scripting and .NET Interactive. Copy this into the interactive tool or source code of the script to reference the package.
// Install deniszykov.WebSocketListener as a Cake Addin
#addin nuget:?package=deniszykov.WebSocketListener&version=4.2.14

// Install deniszykov.WebSocketListener as a Cake Tool
#tool nuget:?package=deniszykov.WebSocketListener&version=4.2.14
The NuGet Team does not provide support for this client. Please contact its maintainers for support.


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. It should work in any operating system running Microsoft.NET/Mono v4.5. This class is perfect for creating endpoints with WebSockets in Windows 2008 or Windows 7, which are not supported by System.Net.WebSockets. Also works on Linux through Mono.

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.

  • It can work with both Text or Binary messages.
  • It supports wss://(secure). More info.
  • It supports per-message deflate compression. More info.
  • It can work with multiple WebSocket standards simultaneously. More info
  • It is extensible. More info.
  • It is asynchronous.
  • It supports Mono. [More info] (//
  • It supports .NET Framework 4.5 and up, NETStandard 1.3 and up and ~~Universal Windows Platform 10 (uap10.0)~~.
  • It has the Ping/Pong functionality built-in.
  • It can measure connection latency. More info
  • It can work with ~~cookies~~ and custom HTTP response statuses. More info
  • It detects and disconnects half open connections.
  • It allows to send and receive messages as streams. WebSocket messages are represented as delimited stream-like objects, that allows integration with other .NET objects like e.g. StreamReader and StreamWriter. Two different WebSocket messages, yield two different streams.
  • Messages reads and writes are streamed. Big messages are not held in memory during reads or writes.
  • It handles partial frames transparently. The WebSocket specification states that a single message can be sent across multiple individual frames. The message stream will allow to read all the message data, no matter if it was sent in a single or multiple frames.
  • It handles interleaved control frames transparently. The WebSocket specification states that control frames can appear interleaved with data frames, including between partial frames of the same message. The message stream will allow to read just the message data, it will skip the control frames.

Take a look on the performance and load tests on a simple 'echo' server.

What's new in v4 (this fork)

This is a fork from project. There is some new features and bug fixes.

Major Features:

  • WebSocketClient

    • Same features and options as WebSocketListener
    • TLS support
    • works with IPv4/IPv6
  • Transports

    • TCP, Unix Sockets, Named Pipes (why not)
    • System.Net.Socket is abstracted as NetworkConnection
    • Graceful disconnection
    • Fine tuning with WebSocketListenerOptions. Fluent confuration API.

Minor Features:

  • Fully async API (it is strongly discouraged to use synchronous API with IO operations)
  • Logging via abstract ILogger
  • No additional dependencies (ServiceModel, TPL Dataflow)
  • New Headers<HeadersT> collections with fast access to known headers
  • Custom BufferManager, and use of BufferManager in all operations with buffers
  • WebSocketListener can now listen multiple endpoints from different transports
  • Pings now processed in batches or could be manually batched and sent (WebSocket.PingAsync)
  • WebSocketMessageWriteStream now can be gracefully closed with CloseAsync()
  • Tested to work under load
  • More unit-tests

Lost Features:

  • UWP target platform (netstandard1.3 is added instead)
  • synchronous IO methods on WebSocket and Streams (Write/Read/Close)
  • Cookies collection on WebSocketHttpRequest (class is still there)
  • Removed potentially dangerous feature 'RemoveBOM' on WSWriteStream.Write and refactored WriteStringAsync(), ReadStringAsync methods to use UTF-8 without BOM

Known Problems:

  • WebSocketDeflateStream uses sync Stream methods, it should be rewritten to fully support async operations.
  • Mono can't handle IPv6 Dual Mode sockets properly (exception in Socket.RemoteEndPoint and Socket.LocalEndPoint).



WebSocketListener is available through NuGet

PM> Install-Package deniszykov.WebSocketListener
There are no supported framework assets in this package.

Learn more about Target Frameworks and .NET Standard.

NuGet packages (3)

Showing the top 3 NuGet packages that depend on deniszykov.WebSocketListener:

Package Downloads

Websocket Connection Capabilities for Buttplug Clients. (.Net Framework 4.7+/.Net Standard 2.0)


Websocket Connection Capabilities for Buttplug Servers. (.Net Framework 4.7+/.Net Standard 2.0)


V8 JavaScript Engine Bindings for Xamarin.Android with Inspector Enabled

GitHub repositories (1)

Showing the top 1 popular GitHub repositories that depend on deniszykov.WebSocketListener:

Repository Stars
[WIP] Ulterius™ server where all the magic happens :rocket: :feelsgood:
Version Downloads Last updated
4.2.14 978 5/15/2021
4.2.10 915 9/8/2020
4.2.9 832 7/3/2020
4.2.8-beta 422 2/27/2020
4.2.7-alpha 597 6/27/2019
4.2.6-alpha 1,047 10/29/2018
4.2.4 35,281 7/3/2018
4.2.2 3,100 3/22/2018
4.1.3 1,573 11/7/2017
4.0.0 2,058 6/21/2017

fixed connection close reason parsing and hung(and timeout) after receiving close frame from client.

added close reply if remote party is requesting connection close.

fixed crash while debug logging Unix Domain Socket connection in `AcceptSocketAsConnection` method.
added additional checks for errord Socket.RemoteEndPoint and Socket.LocalEndPoint, now they produces 'WebSocketHttpRequest.NoAddress'

reverted gzip per-message compression back to original code
added WSClient gzip per-message compression negotiation

fix LocalEndPoint value on WebSocketConnectionRfc6455

[WS] added WriteAndCloseAsync to WebSocketWriteStream
[Compression] added custom async inflater/deflater in WS deflate extension. This would allow make inflation/deflation during WriteAsync/ReadAsync
[WS] replaced extra allocation of Stopwatch with less precise DateTime when measuring negotiation queue
[WS] add int overload to CloseAsync()
[WS] Expose client close codes

[WS] fixed ping timeout error on busy WebSockets

fixed error in WSWriterStream.Dispose() method
reset latency value on WS close or ping timeout
changed WSConnection Dispose() routine. Now it is not waiting for graceful close.
changed Ping timeout now cause WSConnection.Dispose instead on CloseAsync
fixed Ping timeout now properly calculated based on WS activity

[Common] replaced all DynamicMethod invocation with slower reflection alternative in case AOT-only runtime.
[WS] better error message while writing to closed stream
[Transports] clean-up SocketAsyncEventArgs after each operation to prevent holding GC references on used buffers

added DualMode option for TcpTransport
fixed race condition in WebSocket.Write() (Thanks @fuzzykiller)

stable version

fixed ping queue stop on error
added in/out buffers for ping/pong to reduce change of collision if both side pinging
replaced masking/demasking algorithm with faster unsafe implementation
added IpProtectionLevel option for tcp transport
fixed unbserved exception in WSMessageWriteStream.CloseAsync method

removed unused code from helpers
Prevent crash when value contains only empty spaces

added few changes in SendFrameAsync to prevent unobserved exceptions
added better error message for parallel AcceptWebSocketAsync call
added better error message when handshake error occurred

fixed unobserved exception at WebSocketSecureConnectionExtension.ExtendConnectionAsync

fixed infinite loop in timed queue (batch-ping related stuff)

fixed bug in BandwidthSaving ping strategy

added request header to WebSocketClient.ConnectAsync signature
PingQueue list re-use
Echo refactoring (perf. counters removed)
JetBrains.Annotations is now internal

fixed TimedQueue implementation (atomic Int64 reading for 32 bit systems)
fixed Headers add NameValueCollection implementation to threat header values as not splitted headers
removed AsyncResultTask and refactored BeginRead/BeginWrite on streams
updated AsyncQueue implementation

added 'Connection:close' header to 'Bad Request' response of WebSocket handshaker
fixed Unobserved exception because wrong implementation of TaskHelper.IgnoreFault.
refactored TaskHelper.IgnoreFault and TaskHelper.PropagateResutTo to shortcut on Completed tasks
fixed ping errors on WebSockets
fixed TimedQueue impl
Headers refactoring, added HeaderFlags parameter to headers
refactored Socket shutdown sequence to prevent 'connection reset by peer' errors

UNIX Domain Sockets are tested on Linux