Documentation

This is one of the main classes that send a DNS query to your DNS server.

For more advanced usages one can utilize this class directly. The following example looks up the IPv6 address for reactphp.org.

$executor = new TcpTransportExecutor('8.8.8.8:53');

$executor->query(
    new Query($name, Message::TYPE_AAAA, Message::CLASS_IN)
)->then(function (Message $message) {
    foreach ($message->answers as $answer) {
        echo 'IPv6: ' . $answer->data . PHP_EOL;
    }
}, 'printf');

See also example #92.

Note that this executor does not implement a timeout, so you will very likely want to use this in combination with a TimeoutExecutor like this:

$executor = new TimeoutExecutor(
    new TcpTransportExecutor($nameserver),
    3.0
);

Unlike the UdpTransportExecutor, this class uses a reliable TCP/IP transport, so you do not necessarily have to implement any retry logic.

Note that this executor is entirely async and as such allows you to execute queries concurrently. The first query will establish a TCP/IP socket connection to the DNS server which will be kept open for a short period. Additional queries will automatically reuse this existing socket connection to the DNS server, will pipeline multiple requests over this single connection and will keep an idle connection open for a short period. The initial TCP/IP connection overhead may incur a slight delay if you only send occasional queries – when sending a larger number of concurrent queries over an existing connection, it becomes increasingly more efficient and avoids creating many concurrent sockets like the UDP-based executor. You may still want to limit the number of (concurrent) queries in your application or you may be facing rate limitations and bans on the resolver end. For many common applications, you may want to avoid sending the same query multiple times when the first one is still pending, so you will likely want to use this in combination with a CoopExecutor like this:

$executor = new CoopExecutor(
    new TimeoutExecutor(
        new TcpTransportExecutor($nameserver),
        3.0
    )
);

Internally, this class uses PHP's TCP/IP sockets and does not take advantage of react/socket purely for organizational reasons to avoid a cyclic dependency between the two packages. Higher-level components should take advantage of the Socket component instead of reimplementing this socket logic from scratch.