WsAdapter creates two sockets on same server and causes nest to die on ws connection

Bug Report

Current behavior

Creating a new nest instance with ws websocket adapter, nest creates two sockets on the same server. Using nest’s default server booted in main.ts is common getting a websocket connection through this server by upgrading the connection. As I understood the docs, this should be accomplished by just not specifying a port number with the @WebSocketGateway() decorator.

Expected behavior

Allow me to open my socket without crashing nest 😃

Possible Solution

The ws-Adapter runs new websocket.Server(...) twice on the same httpServer in line 37 below: https://github.com/nestjs/nest/blob/2bdcdb5814db144082b0e4107f7b02f9d2d7a720/packages/platform-ws/adapters/ws-adapter.ts#L30-L51

The create-method is called twice in packages/websockets/socket-server-provider.ts

• createSocketServer call Adapter.create https://github.com/nestjs/nest/blob/2bdcdb5814db144082b0e4107f7b02f9d2d7a720/packages/websockets/socket-server-provider.ts#L34
• and then calls createWithNamespace -> getServerOfNamespace -> calls Adapter.create again https://github.com/nestjs/nest/blob/2bdcdb5814db144082b0e4107f7b02f9d2d7a720/packages/websockets/socket-server-provider.ts#L66-L70

The adpter.create()-method is aware that no server should actually be created but the app’s server should be used. In new ws.Server() the socket-server registers for the upgrade-event on the underlaying httpServer. Since two Socket’s are created on this server, both registered upgrade-handlers are fired from the same server-instance and ws throws

Error: server.handleUpgrade() was called more than once with the same socket, possibly due to a misconfiguration
    at WebSocketServer.completeUpgrade (node_modules\ws\lib\websocket-server.js:267:13)
    at WebSocketServer.handleUpgrade (node_modules\ws\lib\websocket-server.js:245:10)
    at Server.upgrade (node_modules\ws\lib\websocket-server.js:89:16)
    at Server.emit (events.js:201:15)
    at onParserExecuteCommon (_http_server.js:580:14)
    at onParserExecute (_http_server.js:520:3)

Edit: The upgrade-handlers are called when a WebSocket trys to connect, not on application startup - and then nest crashes.

Although the error comes from ws it is due to wrong usage by nest.

Environment

Nest version: 7.4.1

[cloakedch]

There were numerous hints from Damien Arrachequesne in the issue tracker that plain ws is the way to go. Today, it may look different again.

[kamilmysliwiec]

In the next major release (v8), this will simply crash during the application bootstrap process, warning you that “namespaces” are no supported by the “ws” package (it’s an exclusive socket.io feature).