Invalid WebSocket frame: RSV1 must be clear

[heiytor]

Description

I am currently facing an issue while trying to connect to my WebSocket server using wscat. Here are the details:

1. Command:

wscat -c ws://localhost:3000/socket.io/\?transport=websocket

2. Error:

Connected (press CTRL+C to quit)
error: Invalid WebSocket frame: RSV1 must be clear]

The same errors occur when I attempt to connect using Postman. However, when I use the ws library, I am able to establish a successful connection. Here's the code:

import express, { Application } from "express";
import socketIO, { Server as SocketIOServer } from "socket.io";
import { createServer, Server as HTTPServer } from "http";
 
class Server {
 private httpServer: HTTPServer;
 private app: Application;
 private io: SocketIOServer;
 
 private readonly DEFAULT_PORT = 3000;
 
 constructor() {
   this.initialize();
   this.handleSocketConnection();
 }
 
 private initialize(): void {
   this.app = express();
   this.httpServer = createServer(this.app);
   // @ts-ignore
   this.io = socketIO(this.httpServer);
 }
 
 private handleSocketConnection(): void {
   this.io.on("connection", socket => {
     console.log("Socket connected.");
   });
 }
 
 public listen(): void {
   this.httpServer.listen(this.DEFAULT_PORT, () => {
    console.log(`port: ${this.DEFAULT_PORT}`)
   });
 }
}

const server = new Server();
 
server.listen();

Environment

• Operating System: Windows 11
• Node.js version: 18.16.0
• Socket.io version: ^4.6.1
• wscat version: 5.2.0

[darrachequesne]

Hi! I think you're missing the EIO=4 query parameter.

See also: https://socket.io/docs/v4/engine-io-protocol/