socket_recvfrom()

(PHP 4 >= 4.1.0, PHP 5, PHP 7)

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

说明

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

The socket_recvfrom() function receives$lenbytes of data in$buffrom$nameon port$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$nameand$portmust be passed by reference. If the socket is not connection-oriented,$namewill be set to the internet protocol address of the remote host or the path to the UNIX socket. If the socket is connection-oriented,$nameis NULL. Additionally, the$portwill contain the port of the remote host in the case of an unconnected AF_INET or AF_INET6 socket.

Note:此函数可安全用于二进制对象。

参数

$socket

The$socketmust 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$lenbytes will be fetched from remote host.

$flags

The value of$flagscan 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,$nameis the path to the file. Else, for unconnected sockets,$nameis 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,$portwill be NULL.

返回值

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.

范例

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.

参见

socket_recv()从已连接的socket接收数据
socket_send()Sends data to a connected socket
socket_sendto()Sends a message to a socket, whether it is connected or not
socket_create()创建一个套接字（通讯节点）

If you use socket_recvfrom on a UDP socket and combine it with the MSG_DONTWAIT flag, it will raise a PHP Warning if there is nothing to read. AFAIK, there is no way around that warning except suppressing it with @ (i.e. you cannot check if there is data before calling socket_recvfrom).

Pay attention! On some PHP version the MSG_DONTWAIT flag is not defined (see https://bugs.php.net/bug.php?id=48326)

MSG_DONTWAIT doesn't seem to exist in windows sockets. However socket_set_nonblock() seems to do the trick.

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.

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);
}
?>