Function upgradeToWebSocket

src/ws-framing.ts:230–262

(
  req: http.IncomingMessage,
  socket: net.Socket,
)

}

export function upgradeToWebSocket(
  req: http.IncomingMessage,
  socket: net.Socket,
): WebSocketConnection {
  const key = req.headers["sec-websocket-key"];
  if (!key) {
    socket.write("HTTP/1.1 400 Bad Request\r\n\r\n");
    socket.destroy();
    throw new Error("Missing Sec-WebSocket-Key header");
  }

  const acceptKey = computeAcceptKey(key);

  let responseHeaders =
    "HTTP/1.1 101 Switching Protocols\r\n" +
    "Upgrade: websocket\r\n" +
    "Connection: Upgrade\r\n" +
    `Sec-WebSocket-Accept: ${acceptKey}\r\n`;

  // Echo back requested subprotocol if present
  const protocol = req.headers["sec-websocket-protocol"];
  if (protocol) {
    // Take the first offered protocol
    const first = protocol.split(",")[0].trim();
    responseHeaders += `Sec-WebSocket-Protocol: ${first}\r\n`;
  }

  responseHeaders += "\r\n";

  socket.write(responseHeaders);

  return new WebSocketConnection(socket);
}