Keepalive

This is a helper for setting proper TCP-Keepalive options and values.

Reason

Common way to enable TCP-Keepalive on a socket looks like this:

socket_set_option($socket, SOL_SOCKET, SO_KEEPALIVE, 1);

And yes, it enables keepalive, but what are keepalive parameters? Example above will use system-default values!

Most systems (OSes) have the following defaults:

Option	Default value	Description
SO_KEEPALIVE	0	TCP Keep-Alive is disabled
TCP_KEEPIDLE	7200	Start keepalive probes after this period (2 hours)
TCP_KEEPINTVL	75	Interval between keepalive probes (75 seconds)
TCP_KEEPCNT	8	Number of keepalive probes before death

So, with default values, first TCP-Keepalive packet will be sent only in 2 hours after last packet, then wait more up to 10 minutes (75s * 8) before dropping dead connection.

Is this really your case?

Not for me, I'd like drop connection within 1 minute or less!

Install

composer require rtm-ctrlz/keepalive

Usage

Below you can find some examples (socket/stream/ssl-stream) for "client-side", but same operations could be done for "server-side".

In examples below we use following parameters:

idle time: 45s
probes interval: 5s
number of probes: 3

So we'd get maximum waiting time of 1 minute.

Raw sockets

// create socket
$socket = \socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
// enable tcp-keepalive
\RtmCtrlz\Keepalive\Keepalive::enable($socket, 45, 5, 3);

Streams (tcp)

// create stream
$stream = \stream_socket_client('tcp://127.0.0.1:80);
// get socket
$socket = \socket_import_stream($stream);
// enable tcp-keepalive
\RtmCtrlz\Keepalive\Keepalive::enable($socket, 45, 5, 3);

Streams (ssl)

This will be a bit harder, because socket_import_stream can not import socket.

But we can do a trick:

create tcp-connection (stream_socket_client())
import socket (socket_import_stream())
enable tcp-keepalive
enable encryption (stream_socket_enable_crypto())

// create stream
// NOTE: stream has "tcp" proto
$stream = \stream_socket_client(
    'tcp://127.0.0.1:443',         // target
    $errno,                        // error number
    $errstr,                       // error description
    1.1,                           // timeout
    STREAM_CLIENT_CONNECT,         // flags
    stream_context_create(         // context
        [
            'ssl' => [
                // ... ssl options
            ],
        ]
    )
);

// get socket
$socket = \socket_import_stream($stream);
// enable tcp-keepalive
\RtmCtrlz\Keepalive\Keepalive::enable($socket, 45, 5, 3);
// enable encryption
\stream_socket_enable_crypto($stream, true, STREAM_CRYPTO_METHOD_TLS_CLIENT);

More examples

See examples directory for more examples.

Gotchas

Option numbers

Unfortunately PHP (and ext-sockets) doesn't have TCP_KEEPIDLE, TCP_KEEPINTVL and TCP_KEEPCNT constants.

Found values

Option	Linux	Darwin	BSD
TCP_KEEPIDLE	`4`	`16`	`256`
TCP_KEEPINTVL	`5`	`257`	`512`
TCP_KEEPCNT	`6`	`258`	`1024`

Linux: Linux tcp.h Darwin: Darwin XNU tcp.h BSD: FreeBSD tcp.h

Windows support

Well, Windows should have support for TCP-Keepalive options, but:

I have no Windows machine to run tests
I didn't look for TCP_KEEP* values on Windows

Feel free to make a PR ;)

rtm-ctrlz/keepalive