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

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.


From Packaged Application
See Releases.

From npm/yarn (for CLI commands)
Run the following in your command line:
# Install Electron globally
npm i -g electron@1.7

# Install wssip global for "wssip" command
npm i -g wssip

# Launch!
yarn: (Make sure the directory in yarn global bin is in your PATH)
yarn global add electron@1.7
yarn global add wssip
You can also run npm install electron (or yarn add electron) inside the installed WSSiP directory if you do not want to install Electron globally, as the app packager requires Electron be added to developer dependencies.

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@1.7
npm i --production

# Start application:
npm 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'}

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