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WSSiP: A WebSocket Manipulation Proxy

Travis-CI Appveyor npm version npm github github release dependency outdated

Short for "WebSocket/ Proxy", this tool, written in Node.js, provides a user interface to capture, intercept, send custom messages and view all WebSocket and Socket.IO communications between the client and server.

Upstream proxy support also means you can forward HTTP/HTTPS traffic to an intercepting proxy of your choice (e.g. Burp Suite or Pappy Proxy) but view WebSocket traffic in WSSiP. More information can be found on the blog post.

There is an outward bridge via HTTP to write a fuzzer in any language you choose to debug and fuzz for security vulnerabilities. See Fuzzing for more details.

Written and maintained by Samantha Chalker (@thekettu). Icon for WSSiP release provided by @dragonfoxing.


From Packaged Application

See Releases.

From npx via npm (for CLI commands)

Run the following in your command line:

npx wssip

From Source

Using a command line:

# Clone repository locally
git clone

# Change to the directory
cd wssip

# If you are developing for WSSiP:
# npm i

# If not... (as to minimize disk space):
npm i electron
npm i --production

# Yarn version:
# yarn add electron
# yarn install --production

# Start application:
npm start
# or yarn:
# yarn start


  1. Open the WSSiP application.
  2. WSSiP will start listening automatically. This will default to localhost on port 8080.
  3. Optionally, use Tools > Use Upstream Proxy to use another intercepting proxy to view web traffic.
  4. Configure the browser to point to http://localhost:8080/ as the HTTP Proxy.
  5. Navigate to a page using WebSockets. A good example is the WS Echo Demonstration.
  6. ???
  7. Potato.


WSSiP provides an HTTP bridge via the man-in-the-middle proxy for custom applications to help fuzz a connection. These are accessed over the proxy server.

A few of the simple CA certificate downloads are:

Get WebSocket Connection Info

Returns whether the WebSocket id is connected to a web server, and if so, return information.

  • URL

    GET http://mitm/ws/:id

  • URL Params


  • Success Response (Not Connected)

    • Code: 200
      Content: {connected: false}
  • Success Response (Connected)

    • Code: 200
      Content: {connected: true, url: 'ws://', bytesReceived: 0, extensions: {}, readyState: 3, protocol: '', protocolVersion: 13}

Send WebSocket Data

Send WebSocket data.

  • URL

    POST http://mitm/ws/:id/:sender/:mode/:type?log=:log

  • URL Params



    sender one of client or server

    mode one of message, ping or pong

    type one of ascii or binary (text is an alias of ascii)


    log either true or y to log in the WSSiP application. Errors will be logged in the WSSiP application instead of being returned via the REST API.

  • Data Params

    Raw data in the POST field will be sent to the WebSocket server.

  • Success Response:

    • Code: 200
      Content: {success: true}
  • Error Response:

    • Code: 500
      Content: {success: false, reason: 'Error message'}


Pull requests are welcomed and encouraged. WSSiP supports the debug npm package, and setting the environment variable DEBUG=wssip:* will output debug information to console.

There are two commands depending on how you want to compile the Webpack bundle: for development, that is npm run compile:dev and for production is npm run compile. React will also log errors depending on whether development or production is specified.

Currently working on:

  • Exposed API for external scripts for fuzzing (99% complete, it is live but need to test more data)
  • Saving/Resuming Connections from File (35% complete, exporting works sans active connections)
  • Using WSSiP in browser without Electron (likely 1.1.0)
  • Rewrite in TypeScript (likely 1.2.0)
  • Using something other than Appbar for Custom/Intercept tabs, and styling the options to center better

For information on using the mitmengine class, see: npm, yarn, or mitmengine/


Application for capturing, modifying and sending custom WebSocket data from client to server and vice versa.








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