Neither websocket nor engine.io connection is cleanly closed

[ladenedge]

I have the following code:

Socket = new SocketIO(....);

// do stuff ..

await Socket.DisconnectAsync();
Socket.Dispose();

The DisconnectAsync() method seems to unsubscribe from the socket.io session, as I would expect:

However, after that I see neither of:

1. An engine.io disconnect ("1")
2. A ClientWebSocket close.

And indeed, my server reports the connection is not cleanly closed:

The remote party closed the WebSocket connection without completing the close handshake.

Am I misusing the library somehow? Looking through the code, it doesn't appear that ClientWebSocket.Close() is ever really called or callable? (I also don't see where the engine.io disconnect is generated, but I'm probably just missing it.) Shouldn't these things just happen when I dispose of the SocketIO class?

What am I doing wrong here?

[doghappy]

From the Fiddler screenshot you provided, we can see that the disconnect message (41/ws,) was sent to the server.
After sending this message, the library should close the WebSocket connection. However, after going through the code,
I couldn't find where the WebSocket is actually closed. probably this is the root cause.

I also tried to reproduce the issue, but I was unable to get the log: The remote party closed the WebSocket connection without completing the close handshake.

Could you please provide the exact steps to reproduce the log you reported?

I started the server with DEBUG logging enabled using:

DEBUG=socket.io* node index

Here are the logs I captured:

[0] 2026-03-13T02:38:38.347Z socket.io:server incoming connection with id 3-3gCSFCBtq844t2AAAC
[0] 2026-03-13T02:38:38.414Z socket.io-parser decoded 0 as {"type":0,"nsp":"/"}
[0] 2026-03-13T02:38:38.414Z socket.io:client connecting to namespace /
[0] 2026-03-13T02:38:38.414Z socket.io:namespace adding socket to nsp /
[0] 2026-03-13T02:38:38.414Z socket.io:socket socket connected - writing packet
[0] 2026-03-13T02:38:38.414Z socket.io:socket join room VL1PiufyYw6Yy8_tAAAD
[0] 2026-03-13T02:38:38.414Z socket.io-parser encoding packet {"type":0,"data":{"sid":"VL1PiufyYw6Yy8_tAAAD"},"nsp":"/"}
[0] 2026-03-13T02:38:38.414Z socket.io-parser encoded {"type":0,"data":{"sid":"VL1PiufyYw6Yy8_tAAAD"},"nsp":"/"} as 0{"sid":"VL1PiufyYw6Yy8_tAAAD"}
[0] 2026-03-13T02:39:08.433Z socket.io-parser decoded 1 as {"type":1,"nsp":"/"}
[0] 2026-03-13T02:39:08.433Z socket.io:socket got packet {"type":1,"nsp":"/"}
[0] 2026-03-13T02:39:08.433Z socket.io:socket got disconnect packet
[0] 2026-03-13T02:39:08.433Z socket.io:socket closing socket - reason client namespace disconnect
[0] 2026-03-13T02:39:38.463Z socket.io:client client close with reason transport close

client code:

using SocketIOClient;
using SocketIOClient.Common;

var io = new SocketIO(new Uri("http://localhost:11400"), new SocketIOOptions
{
    AutoUpgrade = true,
    Transport = TransportProtocol.WebSocket
});
await io.ConnectAsync();

Console.WriteLine("Connected");
await Task.Delay(TimeSpan.FromSeconds(30));
Console.WriteLine("------------1");

await io.DisconnectAsync();
await Task.Delay(TimeSpan.FromSeconds(30));
Console.WriteLine("------------2");
Console.WriteLine("Done");

[ladenedge]

Hm. I am using a custom-built (and very barebones) server, as in #418. Could my server be doing something wrong in this case? It is currently just waiting for the engine.io "1", never receiving it, and my .NET System.Net.WebSockets.WebSocket is producing the error: "The remote party closed the WebSocket connection without completing the close handshake."

From the logs you supplied, it sort of looks like the server is closing the connection when it receives the "41" command? That is not how I understand the protocol, but maybe I'm misreading it? Is the engine.io disconnect ("1") not a thing?

[doghappy]

Based on my experience, 41 indicates that the connection is about to be closed.
I will also add some code to ensure the WebSocket connection is properly closed.

[doghappy]

WebSocket should be closed if you pull the latest code.

[ladenedge]

This works. Thanks for your time and attention!