websocket

name	websocket
description	Specialized skill for WebSocket protocol implementation and testing. Generate RFC 6455 compliant implementations, validate handshake and framing, test with Autobahn Test Suite, implement compression, and debug connection issues.
allowed-tools	Bash(*) Read Write Edit Glob Grep WebFetch
metadata	{"author":"babysitter-sdk","version":"1.0.0","category":"real-time-communication","backlog-id":"SK-005"}

websocket

You are websocket - a specialized skill for WebSocket protocol implementation and testing, providing deep expertise in RFC 6455 compliance, real-time messaging, and performance optimization.

Overview

This skill enables AI-powered WebSocket operations including:

• Generating RFC 6455 compliant implementations
• Validating WebSocket handshake and framing
• Testing with Autobahn Test Suite
• Implementing permessage-deflate compression
• Debugging WebSocket connection issues
• Generating subprotocol handlers
• Analyzing WebSocket traffic

Prerequisites

• WebSocket-capable runtime (Node.js, Python, Go, etc.)
• Optional: wscat or websocat for CLI testing
• Optional: Autobahn Test Suite for compliance testing

Capabilities

1. WebSocket Handshake

Implement RFC 6455 compliant handshake:

const crypto = require('crypto');
const http = require('http');

const WS_MAGIC_STRING = '258EAFA5-E914-47DA-95CA-C5AB0DC85B11';

function computeAcceptKey(secWebSocketKey) {
  return crypto
    .createHash('sha1')
    .update(secWebSocketKey + WS_MAGIC_STRING)
    .digest('base64');
}

function handleUpgrade(req, socket) {
  // Validate upgrade request
  if (req.headers['upgrade']?.toLowerCase() !== 'websocket') {
    socket.end('HTTP/1.1 400 Bad Request\r\n\r\n');
    return false;
  }

  const key = req.headers['sec-websocket-key'];
  if (!key) {
    socket.end('HTTP/1.1 400 Bad Request\r\n\r\n');
    return false;
  }

  // Validate key format (16 bytes base64 encoded)
  const keyBytes = Buffer.from(key, 'base64');
  if (keyBytes.length !== 16) {
    socket.();
     ;
  }

   acceptKey = (key);

  
   requestedProtocols = req.[]?.().( p.()) || [];
   selectedProtocol = (requestedProtocols);

  
   response = [
    ,
    ,
    ,
    
  ];

   (selectedProtocol) {
    response.();
  }

  
   extensions = (req.[]);
   (extensions) {
    response.();
  }

  socket.(response.() + );
   ;
}

 () {
   supported = [, , ];
   requested.( supported.(p)) || ;
}

 () {
  
   (extensionHeader?.()) {
     ;
  }
   ;
}

2. WebSocket Frame Parsing

Parse and create WebSocket frames:

const OPCODES = {
  CONTINUATION: 0x0,
  TEXT: 0x1,
  BINARY: 0x2,
  CLOSE: 0x8,
  PING: 0x9,
  PONG: 0xA
};

class WebSocketFrame {
  constructor() {
    this.fin = true;
    this.rsv1 = false;
    this.rsv2 = false;
    this.rsv3 = false;
    this.opcode = OPCODES.TEXT;
    this.masked = false;
    this.maskingKey = null;
    this.payload = Buffer.alloc(0);
  }

  static parse(buffer) {
    if (buffer.length < 2) return { frame: null, :  };

     frame =  ();
     offset = ;

    
     byte0 = buffer[offset++];
    frame. = (byte0 & ) !== ;
    frame. = (byte0 & ) !== ;
    frame. = (byte0 & ) !== ;
    frame. = (byte0 & ) !== ;
    frame. = byte0 & ;

    
     byte1 = buffer[offset++];
    frame. = (byte1 & ) !== ;
     payloadLength = byte1 & ;

    
     (payloadLength === ) {
       (buffer. < offset + )  { : , :  };
      payloadLength = buffer.(offset);
      offset += ;
    }   (payloadLength === ) {
       (buffer. < offset + )  { : , :  };
      
       high = buffer.(offset);
       low = buffer.(offset + );
      payloadLength = high *  + low;
      offset += ;
    }

    
     (frame.) {
       (buffer. < offset + )  { : , :  };
      frame. = buffer.(offset, offset + );
      offset += ;
    }

    
     (buffer. < offset + payloadLength) {
       { : , :  };
    }

    frame. = buffer.(offset, offset + payloadLength);
    offset += payloadLength;

    
     (frame.) {
      frame. = .(frame.); 
       ( i = ; i < frame..; i++) {
        frame.[i] ^= frame.[i % ];
      }
    }

     { frame, : offset };
  }

  () {
     payloadLength = ..;
     headerLength = ;

     (payloadLength > ) headerLength += ;
      (payloadLength > ) headerLength += ;

     (mask) headerLength += ;

     buffer = .(headerLength + payloadLength);
     offset = ;

    
    buffer[offset++] = (. ?  : ) |
                       (. ?  : ) |
                       (. ?  : ) |
                       (. ?  : ) |
                       .;

    
     lengthByte = mask ?  : ;

     (payloadLength > ) {
      lengthByte |= ;
      buffer[offset++] = lengthByte;
      buffer.(.(payloadLength / ), offset);
      buffer.(payloadLength % , offset + );
      offset += ;
    }   (payloadLength > ) {
      lengthByte |= ;
      buffer[offset++] = lengthByte;
      buffer.(payloadLength, offset);
      offset += ;
    }  {
      lengthByte |= payloadLength;
      buffer[offset++] = lengthByte;
    }

    
     (mask) {
       maskingKey = crypto.();
      maskingKey.(buffer, offset);
      offset += ;

      
       ( i = ; i < payloadLength; i++) {
        buffer[offset + i] = .[i] ^ maskingKey[i % ];
      }
    }  {
      ..(buffer, offset);
    }

     buffer;
  }
}

3. WebSocket Server Implementation

Complete WebSocket server:

const http = require('http');
const crypto = require('crypto');
const EventEmitter = require('events');

class WebSocketServer extends EventEmitter {
  constructor(options = {}) {
    super();
    this.port = options.port || 8080;
    this.maxPayload = options.maxPayload || 100 * 1024 * 1024; // 100MB
    this.clients = new Set();

    this.server = http.createServer((req, res) => {
      res.writeHead(426, { 'Content-Type': 'text/plain' });
      res.end('WebSocket server - upgrade required');
    });

    this.server.on('upgrade', (req, socket, head) => {
      this.handleUpgrade(req, socket, head);
    });
  }

  () {
     key = req.[];
     (!key) {
      socket.();
      ;
    }

     acceptKey = crypto
      .()
      .(key + )
      .();

    socket.([
      ,
      ,
      ,
      ,
      ,
      
    ].());

     client =  (socket, );
    ..(client);

    client.(,  {
      ..(client);
    });

    .(, client, req);
  }

  () {
     ( client  .) {
       (client !== excludeClient && client. === ) {
        client.(message);
      }
    }
  }

  () {
    ..(., callback);
  }

  () {
     ( client  .) {
      client.(, );
    }
    ..(callback);
  }
}

    {
  () {
    ();
    . = socket;
    . = server;
    . = ;
    . = .();
    . = [];

    socket.(,  .(data));
    socket.(,  .());
    socket.(,  .(, err));
  }

  () {
    . = .([., data]);

     (.. > ) {
       { frame, consumed } = .(.);
       (!frame) ;

      . = ..(consumed);
      .(frame);
    }
  }

  () {
     (frame.) {
       .:
       .:
         (frame.) {
           data = frame. === .
            ? frame..()
            : frame.;
          .(, data);
        }  {
          ..(frame);
        }
        ;

       .:
        ..(frame);
         (frame.) {
           firstFrame = .[];
           payload = .(..( f.));
           data = firstFrame. === .
            ? payload.()
            : payload;
          .(, data);
          . = [];
        }
        ;

       .:
        .(frame.);
        ;

       .:
        .(, frame.);
        ;

       .:
         code = ;
         reason = ;
         (frame.. >= ) {
          code = frame..();
          reason = frame..().();
        }
        .(code, reason);
        ;
    }
  }

  () {
     (. !== ) ;

     frame =  ();
     ( data === ) {
      frame. = .;
      frame. = .(data, );
    }  {
      frame. = .;
      frame. = data;
    }

    ..(frame.()); 
  }

  () {
     frame =  ();
    frame. = .;
    frame. = .(data) ? data : .(data);
    ..(frame.());
  }

  () {
     frame =  ();
    frame. = .;
    frame. = .(data) ? data : .(data);
    ..(frame.());
  }

  () {
     (. === ) ;

    . = ;

     frame =  ();
    frame. = .;

     codeBuffer = .();
    codeBuffer.(code, );
     reasonBuffer = .(reason, );
    frame. = .([codeBuffer, reasonBuffer]);

    ..(frame.());
    ..();
  }

  () {
    . = ;
    .();
  }
}

4. permessage-deflate Compression

Implement WebSocket compression:

const zlib = require('zlib');

class PerMessageDeflate {
  constructor(options = {}) {
    this.serverNoContextTakeover = options.serverNoContextTakeover || false;
    this.clientNoContextTakeover = options.clientNoContextTakeover || false;
    this.serverMaxWindowBits = options.serverMaxWindowBits || 15;
    this.clientMaxWindowBits = options.clientMaxWindowBits || 15;

    this.inflateContext = null;
    this.deflateContext = null;
  }

  compress(data, callback) {
    if (!this.deflateContext || this.serverNoContextTakeover) {
      this.deflateContext = zlib.createDeflateRaw({
        windowBits: this.serverMaxWindowBits
      });
    }

    const chunks = [];
    this.deflateContext.on('data', () => chunks.(chunk));
    ..(,  {
       result = .(chunks);
      
       (result. >=  &&
          result[result. - ] ===  &&
          result[result. - ] ===  &&
          result[result. - ] ===  &&
          result[result. - ] === ) {
        result = result.(, -);
      }
      (, result);
    });

    ..(data);
    ..(zlib.);
  }

  () {
     (!. || .) {
      . = zlib.({
        : .
      });
    }

    
     trailer = .([, , , ]);
     input = .([data, trailer]);

     chunks = [];
    ..(,  chunks.(chunk));
    ..(,  {
      (, .(chunks));
    });
    ..(,  (err));

    ..(input);
    ..();
  }
}

5. WebSocket Testing

Test WebSocket implementations:

# Using wscat
wscat -c ws://localhost:8080

# Using websocat
websocat ws://localhost:8080

# Autobahn Test Suite (fuzzing)
docker run -it --rm \
  -v "${PWD}/reports:/reports" \
  -p 9001:9001 \
  crossbario/autobahn-testsuite \
  wstest --mode fuzzingclient --spec /config/fuzzingclient.json

MCP Server Integration

This skill can leverage the following MCP servers for enhanced capabilities:

Server	Description	Integration
MCP-WebSocket Architecture	WebSocket transport with MCP	Real-time AI integration
claude-agent-server	WebSocket server for Claude Agent SDK	Agent orchestration
Claude-Flow	Multi-agent communication via WebSocket	Distributed agents

Best Practices

1. Handle fragmented messages - Large messages may be split across frames
2. Implement heartbeat - Use ping/pong for connection health
3. Set payload limits - Prevent memory exhaustion attacks
4. Close gracefully - Send close frame before disconnecting
5. Validate UTF-8 - Text frames must be valid UTF-8
6. Handle backpressure - Don't overwhelm slow clients

Process Integration

This skill integrates with the following processes:

• websocket-server.js - WebSocket server implementation
• websocket-client.js - WebSocket client implementation
• realtime-messaging-system.js - Real-time messaging architecture

Output Format

When executing operations, provide structured output:

{
  "operation": "test",
  "target": "ws://localhost:8080",
  "status": "success",
  "handshake": {
    "protocol": "graphql-ws",
    "extensions": ["permessage-deflate"]
  },
  "metrics": {
    "messagesReceived": 1000,
    "messagesSent": 1000,
    "avgLatencyMs": 2.5,
    "compressionRatio": 0.65
  },
  "compliance": {
    "rfc6455": true,
    "autobahnPassed": 512
     
  

Constraints

• Follow RFC 6455 strictly for interoperability
• Server must not mask frames (clients must)
• Validate close codes (1000-1015, 3000-4999)
• Handle UTF-8 validation for text frames
• Limit concurrent connections per client