[edit] Last updated: Fri, 28 Jun 2013

socket_recvfrom

(PHP 4 >= 4.1.0, PHP 5)

socket_recvfrom — Receives data from a socket whether or not it is connection-oriented

Description

int socket_recvfrom ( resource $socket , string &$buf , int $len , int $flags , string &$name [, int &$port ] )

The socket_recvfrom() function receives len bytes of data in buf from name on port port (if the socket is not of type AF_UNIX) using socket. socket_recvfrom() can be used to gather data from both connected and unconnected sockets. Additionally, one or more flags can be specified to modify the behaviour of the function.

The name and port must be passed by reference. If the socket is not connection-oriented, name will be set to the internet protocol address of the remote host or the path to the UNIX socket. If the socket is connection-oriented, name is NULL. Additionally, the port will contain the port of the remote host in the case of an unconnected AF_INET or AF_INET6 socket.

Parameters

socket

The socket must be a socket resource previously created by socket_create().

buf

The data received will be fetched to the variable specified with buf.

len

Up to len bytes will be fetched from remote host.

flags

The value of flags can be any combination of the following flags, joined with the binary OR (|) operator.

Possible values for *`flags`*
Flag	Description
`MSG_OOB`	Process out-of-band data.
`MSG_PEEK`	Receive data from the beginning of the receive queue without removing it from the queue.
`MSG_WAITALL`	Block until at least `len` are received. However, if a signal is caught or the remote host disconnects, the function may return less data.
`MSG_DONTWAIT`	With this flag set, the function returns even if it would normally have blocked.

name

If the socket is of the type AF_UNIX type, name is the path to the file. Else, for unconnected sockets, name is the IP address of, the remote host, or NULL if the socket is connection-oriented.

port

This argument only applies to AF_INET and AF_INET6 sockets, and specifies the remote port from which the data is received. If the socket is connection-oriented, port will be NULL.

Return Values

socket_recvfrom() returns the number of bytes received, or FALSE if there was an 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.

Examples

Example #1 socket_recvfrom() example


<?php
error_reporting(E_ALL | E_STRICT);

$socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
socket_bind($socket, '127.0.0.1', 1223);

$from = '';
$port = 0;
socket_recvfrom($socket, $buf, 12, 0, $from, $port);

echo "Received $buf from remote address $from and remote port $port" . PHP_EOL;
?>

This example will initiate a UDP socket on port 1223 of 127.0.0.1 and print at most 12 characters received from a remote host.

Changelog

Version	Description
4.3.0	socket_recvfrom() is now binary safe.


DNS RELAY USING UDP SOCKETS



<?php

 

while(TRUE) {

   $socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP); 

   if($socket === FALSE) 

   { 

       echo 'Socket_create failed: '.socket_strerror(socket_last_error())."\n";

   }

   if(!socket_bind($socketD, "0.0.0.0", 53)) {

       socket_close($socketD);

       echo 'socket_bind failed: '.socket_strerror(socket_last_error())."\n";

   }

   socket_recvfrom($socket,$buf,65535,0,$clientIP,$clientPort);

   $stz = bin2hex($buf);

   $tx = "";

   for($i=0;$i<(strlen($stz)-26-10)/2;$i++)

   {

     $e = "00";

     $e[0] = $stz[$i*2+26];

     $e[1] = $stz[$i*2+27];

     $f = hexdec($e);

     if($f > 0 && $f < 32) $tx .= "."; else

     $tx .= sprintf("%c",$f);

   }

   echo "$clientIP <".$tx.">\n";                                            

   $fp = fsockopen("udp://72.174.110.4",53,$errno,$errstr);

   if (!$fp) 

   {

       echo "ERROR: $errno - $errstr<br />\n";

   } 

   else 

   {

      fwrite($fp,$buf);

      $ret = $buf;

      $ret = fread($fp,667);

      fclose($fp);

   }

  }

socket_send($socket,$ret,667,0);

}

?>

down

-1

jaggerwang at gmail dot com ¶

5 years ago


I'm confused about the rerturn value of socket_recvfrom(), it said -1 when failed, but when I call like this:



if (($len = @socket_recvfrom($sock, $result, 32, 0, $ip, $port)) == -1) {

    if ($this->_debug) {

        echo "socket_read() failed: " . socket_strerror(socket_last_error()) . "\n";

    }

    return false;

}



variable $len = false, when I change the buffer length from 32 to 4096, it becomes right.

down

-1

tsuna at tsunaquack d0t c0m ¶

8 years ago


This function is very handy when dealing with UDP connections, because it enables you to know who's the client who connected to your socket. Bear in mind that UDP doesn't care about the source of the connection, the packets may be annonymous or even faked. No check is required.



If you want to listen on an UDP socket and answer to the client, read my comment on socket_listen() -> http://www.php.net/manual/en/function.socket-listen.php

add a note