socket_create_pair -- Creates a pair of indistinguishable sockets and stores them in an array
Description
bool socket_create_pair ( int domain, int type, int protocol, array &fd )
socket_create_pair() creates two connected and indistinguishable sockets, and stores
them in fd. This function is commonly used in IPC (InterProcess Communication).
The domain parameter specifies the protocol
family to be used by the socket.
Table 1. Available address/protocol families
Domain
Description
AF_INET
IPv4 Internet based protocols. TCP and UDP are common protocols of
this protocol family. Supported only in windows.
AF_INET6
IPv6 Internet based protocols. TCP and UDP are common protocols of
this protocol family. Support added in PHP 5.0.0.
Supported only in windows.
AF_UNIX
Local communication protocol family. High efficiency and low
overhead make it a great form of IPC (Interprocess Communication).
The type parameter selects the type of communication
to be used by the socket.
Table 2. Available socket types
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,
traceroute, etc).
SOCK_RDM
Provides a reliable datagram layer that does not guarantee ordering.
This is most likely not implemented on your operating system.
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.
Table 3. Common protocols
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.
Example 1. socket_create_pair() example
<?php $sockets = array(); /* Setup socket pair */ if (!socket_create_pair(AF_UNIX, SOCK_STREAM, 0, $sockets)) { echo socket_strerror(socket_last_error()); } /* Send and Recieve Data */ if (!socket_write($sockets[0], "ABCdef123\n", strlen("ABCdef123\n"))) { echo socket_strerror(socket_last_error()); } if (!$data = socket_read($sockets[1], strlen("ABCdef123\n"), PHP_BINARY_READ)) { echo socket_strerror(socket_last_error()); } var_dump($data);
/* Close sockets */ socket_close($sockets[0]); socket_close($sockets[1]); ?>
Example 2. socket_create_pair() IPC example
<?php $ary = array(); $strone = 'Message From Parent.'; $strtwo = 'Message From Child.'; if (!socket_create_pair(AF_UNIX, SOCK_STREAM, 0, $ary)) { echo socket_strerror(socket_last_error()); } $pid = pcntl_fork(); if ($pid == -1) { echo 'Could not fork Process.'; } elseif ($pid) { /*parent*/ socket_close($ary[0]); if (!socket_write($ary[1], $strone, strlen($strone))) { echo socket_strerror(socket_last_error()); } if (socket_read($ary[1], strlen($strtwo), PHP_BINARY_READ) == $strtwo) { echo "Recieved $strtwo\n"; } socket_close($ary[1]); } else { /*child*/ socket_close($ary[1]); if (!socket_write($ary[0], $strtwo, strlen($strtwo))) { echo socket_strerror(socket_last_error()); } if (socket_read($ary[0], strlen($strone), PHP_BINARY_READ) == $strone) { echo "Recieved $strone\n"; } socket_close($ary[0]); } ?>
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