(PHP 4 >= 4.1.0, PHP 5, PHP 7)
socket_create — Create a socket (endpoint for communication)
$domain
, int $type
, int $protocol
)Creates and returns a socket resource, also referred to as an endpoint of communication. A typical network connection is made up of 2 sockets, one performing the role of the client, and another performing the role of the server.
domain
The domain parameter specifies the protocol
family to be used by the socket.
| Domain | Description |
|---|---|
AF_INET |
IPv4 Internet based protocols. TCP and UDP are common protocols of this protocol family. |
AF_INET6 |
IPv6 Internet based protocols. TCP and UDP are common protocols of this protocol family. |
AF_UNIX |
Local communication protocol family. High efficiency and low overhead make it a great form of IPC (Interprocess Communication). |
type
The type parameter selects the type of communication
to be used by the socket.
| Type | Description |
|---|---|
SOCK_STREAM |
Provides sequenced, reliable, full-duplex, connection-based byte streams. An out-of-band data transmission mechanism may be supported. The TCP protocol is based on this socket type. |
SOCK_DGRAM |
Supports datagrams (connectionless, unreliable messages of a fixed maximum length). The UDP protocol is based on this socket type. |
SOCK_SEQPACKET |
Provides a sequenced, reliable, two-way connection-based data transmission path for datagrams of fixed maximum length; a consumer is required to read an entire packet with each read call. |
SOCK_RAW |
Provides raw network protocol access. This special type of socket can be used to manually construct any type of protocol. A common use for this socket type is to perform ICMP requests (like ping). |
SOCK_RDM |
Provides a reliable datagram layer that does not guarantee ordering. This is most likely not implemented on your operating system. |
protocol
The protocol parameter sets the specific
protocol within the specified domain to be used
when communicating on the returned socket. The proper value can be
retrieved by name by using getprotobyname(). If
the desired protocol is TCP, or UDP the corresponding constants
SOL_TCP, and SOL_UDP
can also be used.
| Name | Description |
|---|---|
| icmp | The Internet Control Message Protocol is used primarily by gateways and hosts to report errors in datagram communication. The "ping" command (present in most modern operating systems) is an example application of ICMP. |
| udp | The User Datagram Protocol is a connectionless, unreliable, protocol with fixed record lengths. Due to these aspects, UDP requires a minimum amount of protocol overhead. |
| tcp | The Transmission Control Protocol is a reliable, connection based, stream oriented, full duplex protocol. TCP guarantees that all data packets will be received in the order in which they were sent. If any packet is somehow lost during communication, TCP will automatically retransmit the packet until the destination host acknowledges that packet. For reliability and performance reasons, the TCP implementation itself decides the appropriate octet boundaries of the underlying datagram communication layer. Therefore, TCP applications must allow for the possibility of partial record transmission. |
socket_create() returns a socket resource on success,
or FALSE on error. The actual error code can be retrieved by calling
socket_last_error(). This error code may be passed to
socket_strerror() to get a textual explanation of the
error.
If an invalid domain or
type is given, socket_create()
defaults to AF_INET and
SOCK_STREAM respectively and additionally emits an
E_WARNING message.
Took me about 20 minutes to figure out the proper arguments to supply for a AF_UNIX socket. Anything else, and I would get a PHP warning about the 'type' not being supported. I hope this saves someone else time.
<?php
$socket = socket_create(AF_UNIX, SOCK_STREAM, 0);
// code
?>
Note that if you create a socket with AF_UNIX, a file will be created in the filesystem. This file is not removed when you call socket_close - you should unlink the file after you close the socket.
Okay I talked with Richard a little (via e-mail). We agree that getprotobyname() and using the constants should be the same in functionality and speed, the use of one or the other is merely coding style. Personally, we both think the constants are prettier :).
The eight different protocols are the ones implemented in PHP- not the total number in existance (RFC 1340 has 98).
All we disagree on is using 0- Richard says that "accordning to the official unix/bsd sockets 0 is more than fine." I think that since 0 is a reserved number according to RFC 1320, and when used usually refers to IP, not one of it's sub-protocols (TCP, UDP, etc.)
Here's a ping function that uses sockets instead of exec(). Note: I was unable to get socket_create() to work without running from CLI as root. I've already calculated the package's checksum to simplify the code (the message is 'ping' but it doesn't actually matter).
<?php
function ping($host) {
$package = "\x08\x00\x19\x2f\x00\x00\x00\x00\x70\x69\x6e\x67";
/* create the socket, the last '1' denotes ICMP */
$socket = socket_create(AF_INET, SOCK_RAW, 1);
/* set socket receive timeout to 1 second */
socket_set_option($socket, SOL_SOCKET, SO_RCVTIMEO, array("sec" => 1, "usec" => 0));
/* connect to socket */
socket_connect($socket, $host, null);
/* record start time */
list($start_usec, $start_sec) = explode(" ", microtime());
$start_time = ((float) $start_usec + (float) $start_sec);
socket_send($socket, $package, strlen($package), 0);
if(@socket_read($socket, 255)) {
list($end_usec, $end_sec) = explode(" ", microtime());
$end_time = ((float) $end_usec + (float) $end_sec);
$total_time = $end_time - $start_time;
return $total_time;
} else {
return false;
}
socket_close($socket);
}
?>
Please be aware that RAW sockets (as used for the ping example) are restricted to root accounts on *nix systems. Since web servers hardly ever run as root, they won't work on webpages.
On Windows based servers it should work regardless.
Here is a ping function for PHP without using exec/system/passthrough/etc... Very useful to use to just test if a host is online before attempting to connect to it. Timeout is in seconds.
<?PHP
function ping($host, $timeout = 1) {
/* ICMP ping packet with a pre-calculated checksum */
$package = "\x08\x00\x7d\x4b\x00\x00\x00\x00PingHost";
$socket = socket_create(AF_INET, SOCK_RAW, 1);
socket_set_option($socket, SOL_SOCKET, SO_RCVTIMEO, array('sec' => $timeout, 'usec' => 0));
socket_connect($socket, $host, null);
$ts = microtime(true);
socket_send($socket, $package, strLen($package), 0);
if (socket_read($socket, 255))
$result = microtime(true) - $ts;
else $result = false;
socket_close($socket);
return $result;
}
?>
On UNIX systems php needs /etc/protocols for constants like SOL_UDP and SOL_TCP.
This file was missing on my embedded platform.
It took some time to understand how one PHP process can communicate with another by means of unix udp sockets. Examples of 'server' and 'client' code are given below. Server is assumed to run before client starts.
'Server' code
<?php
if (!extension_loaded('sockets')) {
die('The sockets extension is not loaded.');
}
// create unix udp socket
$socket = socket_create(AF_UNIX, SOCK_DGRAM, 0);
if (!$socket)
die('Unable to create AF_UNIX socket');
// same socket will be used in recv_from and send_to
$server_side_sock = dirname(__FILE__)."/server.sock";
if (!socket_bind($socket, $server_side_sock))
die("Unable to bind to $server_side_sock");
while(1) // server never exits
{
// receive query
if (!socket_set_block($socket))
die('Unable to set blocking mode for socket');
$buf = '';
$from = '';
echo "Ready to receive...\n";
// will block to wait client query
$bytes_received = socket_recvfrom($socket, $buf, 65536, 0, $from);
if ($bytes_received == -1)
die('An error occured while receiving from the socket');
echo "Received $buf from $from\n";
$buf .= "->Response"; // process client query here
// send response
if (!socket_set_nonblock($socket))
die('Unable to set nonblocking mode for socket');
// client side socket filename is known from client request: $from
$len = strlen($buf);
$bytes_sent = socket_sendto($socket, $buf, $len, 0, $from);
if ($bytes_sent == -1)
die('An error occured while sending to the socket');
else if ($bytes_sent != $len)
die($bytes_sent . ' bytes have been sent instead of the ' . $len . ' bytes expected');
echo "Request processed\n";
}
?>
'Client' code
<?php
if (!extension_loaded('sockets')) {
die('The sockets extension is not loaded.');
}
// create unix udp socket
$socket = socket_create(AF_UNIX, SOCK_DGRAM, 0);
if (!$socket)
die('Unable to create AF_UNIX socket');
// same socket will be later used in recv_from
// no binding is required if you wish only send and never receive
$client_side_sock = dirname(__FILE__)."/client.sock";
if (!socket_bind($socket, $client_side_sock))
die("Unable to bind to $client_side_sock");
// use socket to send data
if (!socket_set_nonblock($socket))
die('Unable to set nonblocking mode for socket');
// server side socket filename is known apriori
$server_side_sock = dirname(__FILE__)."/server.sock";
$msg = "Message";
$len = strlen($msg);
// at this point 'server' process must be running and bound to receive from serv.sock
$bytes_sent = socket_sendto($socket, $msg, $len, 0, $server_side_sock);
if ($bytes_sent == -1)
die('An error occured while sending to the socket');
else if ($bytes_sent != $len)
die($bytes_sent . ' bytes have been sent instead of the ' . $len . ' bytes expected');
// use socket to receive data
if (!socket_set_block($socket))
die('Unable to set blocking mode for socket');
$buf = '';
$from = '';
// will block to wait server response
$bytes_received = socket_recvfrom($socket, $buf, 65536, 0, $from);
if ($bytes_received == -1)
die('An error occured while receiving from the socket');
echo "Received $buf from $from\n";
// close socket and delete own .sock file
socket_close($socket);
unlink($client_side_sock);
echo "Client exits\n";
?>
Sometimes when you are running CLI, you need to know your own ip address.
<?php
$addr = my_ip();
echo "my ip address is $addr\n";
function my_ip($dest='64.0.0.0', $port=80)
{
$socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
socket_connect($socket, $dest, $port);
socket_getsockname($socket, $addr, $port);
socket_close($socket);
return $addr;
}
?>
I've written the ping() function using socket_create() with SOCK_RAW.
(on Unix System, you need to have the root acces to execute this function)
<?php
/// start ping.inc.php ///
$g_icmp_error = "No Error";
// timeout in ms
function ping($host, $timeout)
{
$port = 0;
$datasize = 64;
global $g_icmp_error;
$g_icmp_error = "No Error";
$ident = array(ord('J'), ord('C'));
$seq = array(rand(0, 255), rand(0, 255));
$packet = '';
$packet .= chr(8); // type = 8 : request
$packet .= chr(0); // code = 0
$packet .= chr(0); // checksum init
$packet .= chr(0); // checksum init
$packet .= chr($ident[0]); // identifier
$packet .= chr($ident[1]); // identifier
$packet .= chr($seq[0]); // seq
$packet .= chr($seq[1]); // seq
for ($i = 0; $i < $datasize; $i++)
$packet .= chr(0);
$chk = icmpChecksum($packet);
$packet[2] = $chk[0]; // checksum init
$packet[3] = $chk[1]; // checksum init
$sock = socket_create(AF_INET, SOCK_RAW, getprotobyname('icmp'));
$time_start = microtime();
socket_sendto($sock, $packet, strlen($packet), 0, $host, $port);
$read = array($sock);
$write = NULL;
$except = NULL;
$select = socket_select($read, $write, $except, 0, $timeout * 1000);
if ($select === NULL)
{
$g_icmp_error = "Select Error";
socket_close($sock);
return -1;
}
elseif ($select === 0)
{
$g_icmp_error = "Timeout";
socket_close($sock);
return -1;
}
$recv = '';
$time_stop = microtime();
socket_recvfrom($sock, $recv, 65535, 0, $host, $port);
$recv = unpack('C*', $recv);
if ($recv[10] !== 1) // ICMP proto = 1
{
$g_icmp_error = "Not ICMP packet";
socket_close($sock);
return -1;
}
if ($recv[21] !== 0) // ICMP response = 0
{
$g_icmp_error = "Not ICMP response";
socket_close($sock);
return -1;
}
if ($ident[0] !== $recv[25] || $ident[1] !== $recv[26])
{
$g_icmp_error = "Bad identification number";
socket_close($sock);
return -1;
}
if ($seq[0] !== $recv[27] || $seq[1] !== $recv[28])
{
$g_icmp_error = "Bad sequence number";
socket_close($sock);
return -1;
}
$ms = ($time_stop - $time_start) * 1000;
if ($ms < 0)
{
$g_icmp_error = "Response too long";
$ms = -1;
}
socket_close($sock);
return $ms;
}
function icmpChecksum($data)
{
$bit = unpack('n*', $data);
$sum = array_sum($bit);
if (strlen($data) % 2) {
$temp = unpack('C*', $data[strlen($data) - 1]);
$sum += $temp[1];
}
$sum = ($sum >> 16) + ($sum & 0xffff);
$sum += ($sum >> 16);
return pack('n*', ~$sum);
}
function getLastIcmpError()
{
global $g_icmp_error;
return $g_icmp_error;
}
/// end ping.inc.php ///
?>
Seems there aren't any examples of UDP clients out there. This is a tftp client. I hope this makes someone's life easier.
<?php
function tftp_fetch($host, $filename)
{
$socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
// create the request packet
$packet = chr(0) . chr(1) . $filename . chr(0) . 'octet' . chr(0);
// UDP is connectionless, so we just send on it.
socket_sendto($socket, $packet, strlen($packet), 0x100, $host, 69);
$buffer = '';
$port = '';
$ret = '';
do
{
// $buffer and $port both come back with information for the ack
// 516 = 4 bytes for the header + 512 bytes of data
socket_recvfrom($socket, $buffer, 516, 0, $host, $port);
// add the block number from the data packet to the ack packet
$packet = chr(0) . chr(4) . substr($buffer, 2, 2);
// send ack
socket_sendto($socket, $packet, strlen($packet), 0, $host, $port);
// append the data to the return variable
// for large files this function should take a file handle as an arg
$ret .= substr($buffer, 4);
}
while(strlen($buffer) == 516); // the first non-full packet is the last.
return $ret;
}
?>
