如果我不在任何地方读取消息，则不会为大猩猩/ websocket调用CloseHandler，最终我只会得到写错误

Question

I have a websocket server using gorilla/websocket.

I have a situation where I am simply writing messages to a set of websockets. My custom CloseHandler is never called when I close the websocket on the browser side.

However, adding a goroutine that calls ReadMessage indefinitely (till some error) leads to the CloseHandler being invoked.

Here's the basic idea: In one goroutine, I run something like this:

for {
    for client := range clients {
        client.stream <- data
    }
    time.Sleep(time.Second)
}

and the other code, called in a separate goroutine, one per client:

go (func() {
    // If I call wsock.ReadMessage here, my CloseHandler works!
})()

for msg := range myclient.stream {
    if err := wsock.WriteMessage(websocket.TextMessage, msg); err != nil {
        break
    }
}

When I close the websocket on the browser side, I expect the CloseHandler to be called, however, it's never called, instead, I eventually get an error on the WriteMessage call.

Answer 1

The close handler is called when a close message is received from the peer. The application must read the connection to receive close and other control messages.

If the application does not read the connection or the peer does not send a close message, then the close handler will not be called.

If your goal is to detect closed connections, then read the connection until an error as returned as shown in the documentation:

func readLoop(c *websocket.Conn) {
    for {
        if _, _, err := c.NextReader(); err != nil {
            c.Close()
            break
        }
    }
 }

The application should only set a close handler when the application must perform some action before the connection bounces the close message back to the peer.