stream_socket_recvfrom()

(PHP 5, PHP 7)

Receives data from a socket, connected or not

说明

stream_socket_recvfrom(resource $socket,int $length[,int $flags= 0[,string &$address]]): string

stream_socket_recvfrom()accepts data from a remote socket up to$lengthbytes.

参数

$socket

The remote socket.

$length

The number of bytes to receive from the$socket.

$flags

The value of$flagscan be any combination of the following:

Possible values for$flags

STREAM_OOB	Process OOB (out-of-band) data.
STREAM_PEEK	Retrieve data from the socket, but do not consume the buffer. Subsequent calls tofread()orstream_socket_recvfrom()will see the same data.

$address

If$addressis provided it will be populated with the address of the remote socket.

返回值

Returns the read data, as a string

范例

Example #1stream_socket_recvfrom()example

<?php
/* Open a server socket to port 1234 on localhost */
$server = stream_socket_server('tcp://127.0.0.1:1234');
/* Accept a connection */
$socket = stream_socket_accept($server);
/* Grab a packet (1500 is a typical MTU size) of OOB data */
echo "Received Out-Of-Band: '" . stream_socket_recvfrom($socket, 1500, STREAM_OOB) . "'\n";
/* Take a peek at the normal in-band data, but don't consume it. */
echo "Data: '" . stream_socket_recvfrom($socket, 1500, STREAM_PEEK) . "'\n";
/* Get the exact same packet again, but remove it from the buffer this time. */
echo "Data: '" . stream_socket_recvfrom($socket, 1500) . "'\n";
/* Close it up */
fclose($socket);
fclose($server);
?>

注释

Note:

If a message received is longer than the$lengthparameter, excess bytes may be discarded depending on the type of socket the message is received from (such as UDP).

Note:

Calls tostream_socket_recvfrom()on socket-based streams, after calls to buffer-based stream functions (likefread()orstream_get_line()) read data directly from the socket and bypass the stream buffer.

参见

• stream_socket_sendto()Sends a message to a socket, whether it is connected or not
• stream_socket_client()Open Internet or Unix domain socket connection
• stream_socket_server()Create an Internet or Unix domain server socket

Note that stream_socket_recvfrom() bypasses stream wrappers including TLS/SSL. While reading from an encrypted stream with fread() will return decrypted data, using stream_socket_recvfrom() will give you the original encrypted bytes.

This method may return a peer address not compatible with stream_socket_sendto() if in ipv6.
The ip returned by recvfrom is not within brackets ([]), and has the port appended, which makes it look like ::1:1234. To cut it properly, use strrpos()

Basically there is currently no real way to determine what the position of the Out of band data is in the tcp/ip stream.
However, it seems that In my current environment (winsock: Windows / PHP 5.3.0) you do not peek beyond the OOB byte unless the buffer is empty
reads do read beyond the OOB data. (I'll check my linux box later)
You should be able to figure out the position of the OOB data by peeking and reading from the regular stream
although it would not be 100% reliable as we do read beyond the OOB data when nothing is in front of it.
depending on the high level protocol it might be possible
to handle the specific "no data in front of out-of-band data" case
<?php
echo "<pre>";
$sockets = stream_socket_pair(STREAM_PF_INET, STREAM_SOCK_STREAM, STREAM_IPPROTO_IP);
$reader=$sockets[0];
$writer=$sockets[1];
stream_socket_sendto($writer,"abc");
stream_socket_sendto($writer,"xyZ",STREAM_OOB); // ONLY THE LAST BYTE IS MARKED AS OOB DATA
stream_socket_sendto($writer,"def");
echo "\r\n";
echo "Test 1, Peeking beyond oob when the read buffer becomes empty\r\n";
echo "The data order is 'abcxyZdef'\r\n";
stream_select($r=array($reader), $w=array(), $x=array($reader),5);
echo "has regular:";var_dump(count($r)!==0);
echo "has oobData:";var_dump(count($x)!==0);
echo "<span style='color:blue' >Peek (9) regular:".stream_socket_recvfrom($reader,9,STREAM_PEEK)."</span>\r\n"; 
echo "<span style='color:green'>Peek (1) OobData:".stream_socket_recvfrom($reader,9,STREAM_OOB|STREAM_PEEK)."</span>\r\n"; 
echo "<span style='color:black'>READ (4) regular:".stream_socket_recvfrom($reader,4)."</span>\r\n"; 
echo "<span style='color:blue' >Peek (9) regular:".stream_socket_recvfrom($reader,9,STREAM_PEEK)."</span>\r\n"; 
echo "<span style='color:black'>READ (1) regular:".stream_socket_recvfrom($reader,1)."</span>\r\n"; 
echo "<span style='color:blue' >Peek (9) regular:".stream_socket_recvfrom($reader,9,STREAM_PEEK)."</span>\r\n"; 
// read the OOB data
echo "<span style='color:red' >READ (9) OobData:".stream_socket_recvfrom($reader,9,STREAM_OOB)."</span>\r\n"; 
echo "<span style='color:blue' >Peek (9) regular:".stream_socket_recvfrom($reader,9,STREAM_PEEK)."</span>\r\n"; 
fclose($sockets[0]);
fclose($sockets[1]);
echo "</pre>";
?>
outputs:
Test 1, Peeking beyond oob when the read buffer becomes empty
The data order is 'abcxyZdef'
has regular:bool(true)
has oobData:bool(true)
Peek (9) regular:abcxy
Peek (1) OobData:Z
READ (4) regular:abcx
Peek (9) regular:y
READ (1) regular:y
Peek (9) regular:def
READ (9) OobData:Z
Peek (9) regular:def
<?php
echo "<pre>";
$sockets = stream_socket_pair(STREAM_PF_INET, STREAM_SOCK_STREAM, STREAM_IPPROTO_IP);
$reader=$sockets[0];
$writer=$sockets[1];
stream_socket_sendto($writer,"Z",STREAM_OOB); // ONLY THE LAST BYTE IS MARKED AS OOB DATA
stream_socket_sendto($writer,"abcxydef");
echo "<hr/>";
echo "\r\n";
echo "Test 2, peek if there is nothing in front of the OOB data\r\n";
echo "The data order is 'Zabcxydef'\r\n";
stream_select($r=array($reader), $w=array(), $x=array($reader),5);
echo "has regular:";var_dump(count($r)!==0);
echo "has oobData:";var_dump(count($x)!==0);
echo "<span style='color:blue'>peek (9) regular:".stream_socket_recvfrom($reader,9,STREAM_PEEK)."</span>\r\n"; 
echo "<span style='color:red' >Peek (9) OobData:".stream_socket_recvfrom($reader,9,STREAM_OOB)."</span>\r\n"; 
echo "<span style='color:blue'>peek (9) regular:".stream_socket_recvfrom($reader,9,STREAM_PEEK)."</span>\r\n"; 
echo "</pre>";
?>
Outputs: 
Test 2, peek if there is nothing in front of the OOB data
The data order is 'Zabcxydef'
has regular:bool(true)
has oobData:bool(true)
peek (9) regular:abcxydef
Peek (9) OobData:Z
peek (9) regular:abcxydef