如何使用ws.SetWriteDeadline？

Question

When I close a browser I want to disconnect a websocket in 3 seconds instead of 1 minute. The following just keep writing into a void without error until the tcp ip timeout I guess, not the SetWriteDeadline.

f := func(ws *websocket.Conn) {
    for {
        select {
        case msg := <-out:
            ws.SetWriteDeadline(time.Now().Add(3 * time.Second))
            if _, err := ws.Write([]byte(msg)); err != nil {
                fmt.Println(err)
                return
            }
        case <-time.After(3 * time.Second):
            fmt.Println("timeout 3")
            return
        }
    }
}
return websocket.Handler(f)

I need to wait for this err

write tcp [::1]:8080->[::1]:65459: write: broken pipe

before it finally closes the connection, which takes about a minute or more.

Answer 1

You are you using WriteDeadline correctly. The deadline specifies the time for writing data to the TCP stack's buffers, not the time that the peer receives the data (if it does at all).

To reliably detect closed connections, the application should send PINGs to the peer and wait for the expected PONGs. The package you are using does not support this functionality, but the Gorilla package does. The Gorilla chat application shows how use PING and PONG to detect closed connections.