socket_recv

(PHP 4 >= 4.1.0, PHP 5, PHP 7, PHP 8)

socket_recv — Recibe información desde un socket conectado

Descripción

socket_recv(
    resource $socket,
    string &$buf,
    int $len,
    int $flags
): int

La función socket_recv() recibe len bytes de información en buf desde socket. socket_recv() se puede usar para reunir información desde sockets conectados. Además, se pueden especificar una o más banderas para modificar el comportamiento de la función.

buf es pasado por referencia, por lo que debe ser especificado como una variable en la lista de argumentos. La información leída desde socket por socket_recv() será devuelta en buf.

Parámetros

socket

socket debe ser un recurso socket previamente creado por socket_create().

buf

La información recibida será traida a la variable especifivada por buf. Si ocurre un error, si la conexión es reiniciada, o si no hay información disponible, buf será establecido a null.

len

Se obtendrán hasta len bytes desde el host remoto.

flags

El valor de flags puede ser una combinación de las siguientes banderas, unidas con el operador binario OR (|).

**Valores posibles de `flags`**
Bandera	Descripción
`MSG_OOB`	Procesar información fuera de banda.
`MSG_PEEK`	Recibir informaicón desde el inicio de la cola recibida sin eliminarla de la cola.
`MSG_WAITALL`	Bloquea hasta que al menos se reciba `len` bytes. Sin embargo, si se captura una señal o el host remoto se desconecta, la función puede devolver menos información.
`MSG_DONTWAIT`	Con esta bandera establecida, la función devuelve incluso si normalmente habría bloqueado.

Valores devueltos

socket_recv() devuelve el número de bytes recibidos, o false si hubo un error. El código de error real se puede recuperar llamando a socket_last_error(). Este código de error se puede pasar a socket_strerror() para obtener una explicación textual del error.

Ejemplos

Ejemplo #1 Un ejemplo de socket_recv()

Este ejemplo es un reescrito sencillo del primer ejemplo de Ejemplos para usar socket_recv().

<?php
error_reporting(E_ALL);

echo "<h2>Conexión TCP/IP</h2>\n";

/* Obtener el puerto del servicio WWW. */
$service_port = getservbyname('www', 'tcp');

/* Obtener la dirección IP del host objetivo. */
$address = gethostbyname('www.example.com');

/* Crear un socket TCP/IP. */
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
if ($socket === false) {
    echo "socket_create() falló: razón: " . socket_strerror(socket_last_error()) . "\n";
} else {
    echo "OK.\n";
}

echo "Intentando conectar a '$address' en el puerto '$service_port'...";
$result = socket_connect($socket, $address, $service_port);
if ($result === false) {
    echo "socket_connect() falló.\nRazón: ($result) " . socket_strerror(socket_last_error($socket)) . "\n";
} else {
    echo "OK.\n";
}

$in = "HEAD / HTTP/1.1\r\n";
$in .= "Host: www.example.com\r\n";
$in .= "Connection: Close\r\n\r\n";
$out = '';

echo "Enviando petición HTTP HEAD...";
socket_write($socket, $in, strlen($in));
echo "OK.\n";

echo "Leyendo la respuesta:\n\n";
$buf = 'Este es mi buffer.';
if (false !== ($bytes = socket_recv($socket, $buf, 2048, MSG_WAITALL))) {
    echo "Leídos $bytes bytes desde socket_recv(). Cerrando el socket...";
} else {
    echo "socket_recv() falló; razón: " . socket_strerror(socket_last_error($socket)) . "\n";
}
socket_close($socket);

echo $buf . "\n";
echo "OK.\n\n";
?>

El ejemplo de arriba producirá algo parecido a esto:

<h2>Conexión TCP/IP</h2>
OK.
Intentando conectar a '208.77.188.166' en el puerto '80'...OK.
Enviando petición HTTP HEAD...OK.
Leyendo la respuesta:

Leídos 123 bytes desde socket_recv(). Cerrando el socket...HTTP/1.1 200 OK
Date: Mon, 14 Sep 2009 08:56:36 GMT
Server: Apache/2.2.3 (Red Hat)
Last-Modified: Tue, 15 Nov 2005 13:24:10 GMT
ETag: "b80f4-1b6-80bfd280"
Accept-Ranges: bytes
Content-Length: 438
Connection: close
Content-Type: text/html; charset=UTF-8

OK.

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User Contributed Notes 13 notes

down

dgk at tcde dot ru ¶

20 years ago


I've used socket_select and socket_recv with a while loop and found myself in trouble when remote side closed connection. The code below produced infinite loop and socket_select returned immediately (which lead to high cpu time consumption).

<?

socket_set_nonblock($my_socket);
$streams = array($my_socket/*, ... */);

$lastAccess = time();
while (socket_select($streams, $write = NULL, $except = NULL, SLEEP_TIME_SECONDS, SLEEP_TIME_MILLISECONDS) !== FALSE) {
    if (in_array($my_socket, $streams)) {
        while (@socket_recv($my_socket, $data, 8192, 0)) {
            echo $data;
        }
        $lastAccess = time();
    } else {
        if (time()-$lastAccess > LAST_ACCESS_TIMEOUT) {
            break;
        }
    }
    // ...
    $streams = array($my_socket/*, ... */);
}

?>

The solution was simple, but quite hard to find because socket_recv is not documented. socket_recv returns FALSE if there is no data and 0 if the socket is widowed (disconnected by remote side). So I had just to check return value of socket_recv. The problem now sounds stupid, but I've spend some time to find it out.
I hope this will save some of somebody's hair ;)

down

ss-130 at yandex dot ru ¶

11 years ago


<?php
$er = error_reporting(0);
$bytes    = socket_recv($socket,$buffer,1,MSG_WAITALL);
error_reporting($er);

// MEGA BUG HERE
// this statuses are wrong and swapped, closed socket must be with "FALSE"
// but in fact he swap the values:
// http://php.net/manual/en/function.socket-recv.php
// 
if($bytes===false){ // no data available, socket not closed
    echo 'WS_READ_ERR1: '.socket_strerror(socket_last_error($socket)).PHP_EOL;
    // print when no data available:
    // WS_READ_ERR1: Resource temporarily unavailable
    continue;
}else if($bytes===0){ // socket closed
    echo 'WS_READ_ERR2: '.socket_strerror(socket_last_error($socket)).PHP_EOL;
    // print when socket closed:
    // WS_READ_ERR2: Success
    $process->close();
}

?>

down

m_lajos at hotmail dot com ¶

10 years ago


Workaround for the missing MSG_DONTWAIT flag according to the bug report page:

<?php if(!defined('MSG_DONTWAIT')) define('MSG_DONTWAIT', 0x40); ?>

down

rathamahata at rathamahata dot net ¶

19 years ago


It looks like that mysterious flags are just the recv(2) flags passed to your OS syscall and nothing more...

ext/sockets/sockets.c:PHP_FUNCTION(socket_recv)
...
        if ((retval = recv(php_sock->bsd_socket, recv_buf, len, flags)) < 1) {
                efree(recv_buf);
...

for linux you can type `man 2 recv' and you will see complete description of thouse flags.

Sergey S. Kosrtyliov <rathamahata@rathamahata.net>
http://www.rathamahata.net/

down

bastiaan at [no-spam] megabass dot nl ¶

20 years ago


in case you want to empty/unset $buffer, but failing to do so, try using 0 as flag.
PHP_NORMAL_READ and PHP_BINARY_READ respectively hold 1 and 2 as value.

down

davide dot renzi at gmail dot com ¶

12 years ago


In PHP version 5.* there is a bug: MSG_DONTWAIT flag is not defined (see https://bugs.php.net/bug.php?id=48326)

down

lexkrstn at gmail dot com ¶

6 years ago


It seems like the flags are just passed to the underlying recv() function of your OS, hence there no MSG_DONTWAIT flag on Windows and you should not define it yourself in that case, it just won't work.

down

-1

Anonymous ¶

3 years ago


<?php

namespace Safe;

use Safe\Exceptions\SocketsException;

/**
 * After the socket socket has been created
 * using socket_create, bound to a name with
 * socket_bind, and told to listen for connections
 * with socket_listen, this function will accept
 * incoming connections on that socket. Once a successful connection
 * is made, a new socket resource is returned, which may be used
 * for communication. If there are multiple connections queued on
 * the socket, the first will be used. If there are no pending
 * connections, socket_accept will block until
 * a connection becomes present. If socket
 * has been made non-blocking using
 * socket_set_blocking or
 * socket_set_nonblock, FALSE will be returned.
 *
 * The socket resource returned by
 * socket_accept may not be used to accept new
 * connections. The original listening socket
 * socket, however, remains open and may be
 * reused.
 *
 * @param resource $socket A valid socket resource created with socket_create.
 * @return resource Returns a new socket resource on success. The actual
 * error code can be retrieved by calling
 * socket_last_error. This error code may be passed to
 * socket_strerror to get a textual explanation of the
 * error.
 * @throws SocketsException
 *
 */
function socket_accept($socket)
{
    error_clear_last();
    $result = \socket_accept($socket);
    if ($result === false) {
        throw SocketsException::createFromPhpError();
    }
    return $result;
}

/**
 * Create a Socket resource, and bind it to the provided AddrInfo resource.  The return
 * value of this function may be used with socket_listen.
 *
 * @param resource $addr Resource created from socket_addrinfo_lookup.
 * @return resource Returns a Socket resource on success.
 * @throws SocketsException
 *
 */
function socket_addrinfo_bind($addr)
{
    error_clear_last();
    $result = \socket_addrinfo_bind($addr);
    if ($result === null) {
        throw SocketsException::createFromPhpError();
    }
    return $result;
}

down

Anonymous ¶

19 years ago


I'm glad that Bastion left the above post about the mysterious int flag. He just helped to fix a problem that I've spent six hours on. Here's my code:

for($ct=1; $ct<=$numrecs; $ct++) {
     $rec = "";
     $nr=socket_recv($fp,$rec,77,0);
     print "Rec # $ct -->";
         print "$rec";
         print "<br>";
      }

The code is pretty simple, it just loops through all my records and prints them out. All records are 77 bytes and all end with a period. The first 36 records print perfectly then at 37 things go bad. The records start to get offset. The last few characters of the 37th record end up printing on the 38th record. The data on the sending side was perfect, so I knew that the problem was with socked_recv.

After reading the above post I tried changing the int flag. Changing the flag to 2 worked:
$nr=socket_recv($fp,$rec,77,2);

Now everything lines up perfectly. I had always left int flag as 0 since it's undocumented. 

Martin K.

down

-1

Anonymous ¶

19 years ago


My last post was incorrect. The int flag set to 2 apparently reset the file position pointer so what I was reading was the first record repeatedly. 

My workaroud ended up being the following:

for($ct=1; $ct<=$numrecs; $ct++) {
    $rec = "";
    $nr=socket_recv($fp,$rec,76,0);
        
    //grab the extra bytes.
    $terminator = "";
    while ($terminator != ".") {
        $nr=socket_recv($fp,$terminator,1,0);
    }
    
     $custarray[]=substr($rec,0,76);         
}

Martin K.

down

-2

engine at [NO SPAM] illusiononly dot com ¶

20 years ago


To read from socket both on linux and windows OS having  flash as a client I use function bellow. $length is the size of  a chunk, not the max length to read. It will continue reading until EOL char  occures or client disconnects (or in case of error), so it works for bigger packets as well.

     function read($descriptor, $length = 1024) {
            $this->method = "read";
            if(!$client){
                echo("No valid socket descriptor !\n");
                return false;
            }
            $read ='';
        while(($flag=socket_recv($descriptor, $buf, $length,0))>0){
              $asc=ord(substr($buf, -1));
            if ($asc==0) {
                $read.=substr($buf,0,-1);
                break;
            }else{
                $read.=$buf;
            }
        }
           if ($flag<0){
            //error
            return false;
        }elseif ($flag==0){
            //Client disconnected
            return  false;
        }else{
              return $read;
        }

     }

down

-3

cottton at i-stats dot net ¶

10 years ago


socket_recv()
returns FALSE if client returned no data
returns 0 (zero) if client disconnected

also (asuming case socket_select() "gave" us a "changed" socket):
if 
socket_recv() returned FALSE 
and no bytes were received 
then
client "crashed" (call it disconnected).

else if
socket_recv() returned 0 (zero) 
and no bytes were received 
then
client "normaly" disconnected.

Im pretty sure -- 99.99%.
Example:
<?php
function receive($socket)
{
    // !
    // on all following cases we assume that
    // socket_select() returned the current socket as "changed"
    // !

    $timeout = 3; // set your timeout

    /* important */
    $socket_recv_return_values['no_data_received'] = false;
    $socket_recv_return_values['client_disconnected'] = 0;

    $start = time();
    $received_data = null;
    $received_bytes = null;
    socket_set_nonblock($socket);
    socket_clear_error();
    while(
        ($t_out=((time()-$start) >= $timeout)) === false
        and ($read=@socket_recv($socket, $buf, 4096, 0)) >= 1
    ){
        $received_data  = (isset($received_data)) ? $received_data . $buf : $buf;
        $received_bytes = (isset($received_bytes)) ? $received_bytes + $read : $read;
    }
    $last_error = socket_last_error($socket);
    socket_set_block($socket);

    if($t_out === true){
        throw new Exception(
            'timeout after ' . ((!$received_bytes) ? 0 : $received_bytes) . ' bytes',
            0 // your eCode here
        );
    }
    elseif($last_error !== false and $last_error !== 0){
        throw new Exception(
            socket_strerror($last_error),
            $last_error
        );
    }
    else{
        if($read === $socket_recv_return_values['no_data_received']){
            // client returned NO DATA
            // but we were in a loop and could have got some data before:
            if($received_bytes < 1){
                // client is connected but sent NO DATA ?
                // no:
                // in this case the client must be "crashed" because -
                // it is not possible to "send no data" (zero bytes)
                // socket_select() now returns this socket as "changed" "forever"
                throw new Exception(
                    'client crashed',
                    0 // your eCode here
                );
            }else{
                // client returned DATA
                return $received_data;
            }
        }
        elseif($read === $socket_recv_return_values['client_disconnected']){
            // client disconnected
            if($received_bytes < 1){
                // client disconnected before/without sending any bytes
                throw new Exception(
                    'client disconnected',
                    0 // your eCode here
                );
            }
            else{
                // *this value* ^= $socket_recv_return_values['client_disconnected']
                //
                // client disconnected AFTER sending data (we were in a loop!)
                // socket_select() will return this socket "forever" as "changed" and -
                // socket_recv() will return *this value* "forever".
                // we will be "back" again "very soon" to see:
                //  socket_recv() returns *this value* AND no bytes received
                //  which results in disconnect-exception above
                return $received_data;
            }
        }
    }
}
?>

down

-3

e-vela at bol dot com dot br ¶

7 years ago


Usage example for MSG_PEEK: this function tells if the socket has data available to be read, but preserving it to be read at a future moment.

<?php
// Workaround for the missing define
if(!defined('MSG_DONTWAIT')) define('MSG_DONTWAIT', 0x40);

// Function to check if there is data available in the socket
function SocketHasData($socket) {
    // Based on the following fact:
    // $result=0 -> disconnected, $result=false -> no data

    $data = ''; // We need a buffer, but we won't use it

    // MSG_PEEK means to preserve data in the queue, so it can
    // actually be read afterwards
    $result = socket_recv($socket, $data, 1, MSG_PEEK | MSG_DONTWAIT );

    if ($result === false) return false; // If no data, returns false
    return true; // Otherwise returns true
}
?>

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