websocket closes connection after 30 seconds

[David Liu]

Hi guys,

I am seeing an issue with civet's websocket where it always disconnects my client connection after 30 seconds. I've tried chrome and safari and both have same behavior

The part of the code that complains is inside read_websocket

             /* Read from the socket into the next available location in the
               message queue. */
            if ((n = pull(NULL, conn, conn->buf + conn->data_len,
                          conn->buf_size - conn->data_len)) <= 0) {
                /* Error, no bytes read */
                break;
            }

pull returns -1 after 30 seconds and then the connection is closed. I thought websocket is supposed to have some keep alive mechanism.

Any help is appreciated.

David 

[bel]

Did you set the "request_timeout_ms" config parameter?
It's default value is 30000, so every socket that is idle for 30 seconds will be closed

You could increase this value and/or send a message from the client to the the websocket connection every 10 seconds.

[David Liu]

bel,

Thanks that was it. Is it reasonable to set this value to 0?

David

[bel]

On Saturday, November 16, 2013 8:10:16 PM UTC+1, David Liu wrote:

Is it reasonable to set this value to 0?

In theory:
Deactivating the timeout would be the TCP standard (HTTP is based on TCP). A TCP connection may stay established even for weeks without any traffic.

In practice:
Every connection binds some resources in the server - in the current implementation it uses one thread, there are 50 threads in the current default configuration, you can change it with the num_threads config option, but increasing it to several hundred would not be a good idea. If you do have the server in a closed environment (home network, small company network, ..) and you can restart the server from time to time, you will probably not run into any problems. Otherwise you may reach a state where all available threads are blocked by connections that may be actually broken, but the server can not know that they are no longer open at the client side. Furthermore, at least in larger networks and the internet, there are often different network components that still use a timeout, typically a few minutes up to two hours, so setting a longer timeout in the server will not have any positive effect anymore - the idle connections will be reset by these components (e.g. proxies, firewalls, modems, ..) anyway, while the server will still consider them as open. So I would not use a timeout of more than two hours.

My recommendation:
When using websockets, you always implement some protocol on top of them - message in some format are passed from server to client and from client to server. Just send some "still alive" message from the client to the server every 10 seconds. Or increase the timeout to a few minutes and send a "still alive" message every minute.