socket_read

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

socket_read — Lee un máximo de longitud de bytes desde un socket

Descripción

socket_read(resource $socket, int $length, int $type = PHP_BINARY_READ): string

La función socket_read() lee desde un recurso socket socket creado por las funciones socket_create() o socket_accept().

Parámetros

socket

Un recurso socket válido creado con socket_create() o socket_accept().

length

El número máximo de bytes leidos es especificado por el parámetro length. Por lo demás se puede usar \r, \n, o \0 para finalizar la lectura (dependiendo del parámetro type, véase abajo).

type

El parámetro opcional type es una constante nominada:

PHP_BINARY_READ (Predeterminada) - usa la función del sistema recv(). Segura para la lectura de información binaria.
PHP_NORMAL_READ - la lectura se detiene en \n o \r.

Valores devueltos

socket_read() devuelve la información como cadena en caso de éxito, o false en caso de error (incluyendo si el host remoto cerró la conexión). El código de error real se puede recuperar llamando a socket_last_error(). Este código se puede pasar a socket_strerror() para obtener una explicación textual del error.

Nota:
socket_read() devuelve una cadena de longitud cero ("") cuando no hay más información que leer.

Ver también

socket_accept() - Acepta una conexión de un socket
socket_bind() - Vincula un nombre a un socket
socket_connect() - Inicia una conexión sobre un socket
socket_listen() - Escucha una conexión sobre un socket
socket_last_error() - Devuelve el último error sobre un socket
socket_strerror() - Devuelve una cadena que describe un error de socket
socket_write() - Escribir en un socket

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User Contributed Notes 21 notes

down

cottton at i-stats dot net ¶

10 years ago


quote:
"Note:
socket_read() returns a zero length string ("") when there is no more data to read."

This is not true!

In a while loop  
(example case few bytes to receive - just enough for 1 call, but you use a loop to be sure you received all data)
if you use 
<? socket_set_block($socket); ?>
you will get:
1st call in loop: data
2nd call in loop: a block forever, if there isnt data anymore or w/e happen to the "other side"

So ofc you want to use 
<? socket_set_nonblock($socket); ?>
and you will get:
1st call in loop: data
2nd call in loop: socket_read() returns FALSE (bool) and socket_last_error() gives you a SOCKET_EWOULDBLOCK (http://de1.php.net/manual/de/sockets.constants.php)

There is not a single time i got a empty string back from socket_read.
And im "working" on this problem(bug?) since a week or so.

You better use socket_recv() instead.
(good luck)

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nuitari-php at nuitari dot net ¶

17 years ago


PHP_NORMAL_READ - reading stops at \n or \r.

This seems to be meant literally.
If there is a \r, then it will stop reading, even if there is a \n right after it. You have to call the read again just to get rid of the \n.

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dotpointer ¶

17 years ago


PHP 5.2.0 / Win32 / Apache 1.3 - It seems like...

PHP_BINARY_READ - works, but returns '', not FALSE...
- is blocking, until data received or connection closed
- does pass-through \r\n etc.
- returns data on data, '' on connection closed
- you can detect closed connection by checking for '' (not FALSE as stated i manual)

PHP_NORMAL_READ - not working so good...
- is non-blocking
- does not pass-through \r\n etc.
- returns false on no-data, false on connection closed :(
- (no way here to detect a closed connection...?)
- (is this a bug? http://bugs.php.net/bug.php?id=21880 )
- (is this a bug? http://bugs.php.net/bug.php?id=21197 )
- (could not get data from this option at all in fact...)

PHP_BINARY_READ seems to be the "right way to go" 
for now. Both checking for '' and false to detect closed 
connection is probably smart, as this "bug"(?) may 
be fixed...

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berniev ¶

7 years ago


It is not obvious from the docs or notes...
PHP_NORMAL_MODE is different to PHP_BINARY in that the former blocks regardless of socket_set_nonblock, the latter respects block and nonblock.

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michi at tr51 dot org ¶

20 years ago


if you'd like to make a "socket_read" on a linux-system connected with a flash-client (v. 6.0 r81) you have to send a string to the connected port:

<?php

   ...  //initialising communication

    $string = "ready to get/send data\0"; 
    socket_write($socket, $string);

    //now you can read from...
    $line = trim(socket_read($socket, MAXLINE));

    ...  // do some stuff, finaly close connection
?>

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Anonymous ¶

22 years ago


Windows telnet sends/recieves one character at a time. Try adding PHP_NORMAL_READ to the end of socket_read, that might help.

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nad0r1 at hush dot ai ¶

17 years ago


Another way to bypass the annoying thing with telnet, that send each character as a string ,is to check if the response is "\r\n", that is the string that telnet sends when the user presses enter.

Here is an example:
<?php
error_reporting(E_ALL);

/* Allow the script to hang around waiting for connections. */
set_time_limit(0);

/* Turn on implicit output flushing so we see what we're getting
 * as it comes in. */
ob_implicit_flush();

$address = '127.0.0.1';
$port = 100;

if (($sock = socket_create(AF_INET, SOCK_STREAM, SOL_TCP)) === false) {
    echo "socket_create() failed: reason: " . socket_strerror(socket_last_error()) . "\n";
}

if (socket_bind($sock, $address, $port) === false) {
    echo "socket_bind() failed: reason: " . socket_strerror(socket_last_error($sock)) . "\n";
}
else 
  echo 'Socket ' . $address . ':' . $port . " has been opened\n";

if (socket_listen($sock, 5) === false) {
    echo "socket_listen() failed: reason: " . socket_strerror(socket_last_error($sock)) . "\n";
}
else 
   echo "Listening for new clients..\n";

   $client_id = 0;
do {
    if (($msgsock = socket_accept($sock)) === false) {
        echo "socket_accept() failed: reason: " . socket_strerror(socket_last_error($sock)) . "\n";
        break;
    }
    else {
        $client_id += 1;
      echo "Client #" .$client_id .": Connect\n";
    }
      
    /* Send instructions. */
    $msg = "\nWelcome to the PHP Test Server. \n" .
        "To quit, type 'quit'. To shut down the server type 'shutdown'.\n";
    socket_write($msgsock, $msg, strlen($msg));
$cur_buf = '';
    do {
        if (false === ($buf = socket_read($msgsock, 2048))) {
            echo "socket_read() failed: reason: " . socket_strerror(socket_last_error($msgsock)) . "\n";
            break 2;
        }
        if ($buf == "\r\n") {
        if ($cur_buf == 'quit') {
            echo 'Client #' .$client_id .': Disconnect' . "\n";
            break;
        }
        if ($cur_buf == 'shutdown') {
            socket_close($msgsock);
            break 2;
        }
        //else {
       $talkback = "Unknown command: " . str_replace("\r\n", '\r\n', $cur_buf) ."\n";
       socket_write($msgsock, $talkback, strlen($talkback));
       // }
        echo 'Client #' .$client_id .': ' . $cur_buf . "\n"; 
        $cur_buf = '';
        }
        else $cur_buf .= $buf;
    } while (true);
    socket_close($msgsock);
} while (true);

socket_close($sock);
?>

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d dot bergloev at gmail dot com ¶

5 years ago


Binary read is the correct way to read data in most cases, whereas "normal read", is a strange and lazy PHP built mode, that works mostly with terminal data. 

If you want to keep track of closed connections with binary read, the correct way is NOT to switch from binary to "normal", like some suggests. The correct way is to create some test scenarios and see how PHP deals with specific circumstances. 

Here is what a quick test shows, when working with non-blocking sockets. 

<?php
$input = socket_read($socket, 1024);

// In most cases, error produces an empty string and not FALSE
if ($input === FALSE || strcmp($input, '') == 0) {
    $code = socket_last_error($socket);

    // You MUST clear the error, or it will not change on next read
    socket_clear_error($socket);

    if ($code == SOCKET_EAGAIN) {
        // Nothing to read from non-blocking socket, try again later...

    } else {
        // Connection most likely closed, especially if $code is '0'
    }

} else {
    // Deal with the data
}
?>

There are more errors to consider, but this will get you started.

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Arvy ¶

6 years ago


On non-blocking sockets, the function will return "" if no data is received, and even if the client disconnects.

If you want to check if the client disconnected, use ===.

$ret=socket_read($socket);

$ret=="" : connected but no data received or client disconnected
$ret==="" : client disconnected for sure

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dhaubert dot ti at gmail dot com ¶

9 years ago


A way to wait for a message response by the socket or take the first message incoming.

Note that if the server turn offline, you have a socket resource, but while trying socket_read(), it gives you a warning message that will fill your hard drive kickly due to logging.

The example above try read the message at best 3 times, 3 seconds sleeping for another reading. 
<?php
function waitResponse($response = "") {
   $status = "";
   $tries = 3;
   $counter = 0;
   while ($status == $response) {
            $status = socket_read($socket, 1024);
            if(!$status){
               if($counter >= $tries){
                  break;
               }else{
                  $counter++;
                  sleep(3);
               }
            }
   }
return $response;
}

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eng.mrkto.com ¶

13 years ago


It seems like in socket_* functions in BLOCKING mode where is no way to check if more than $length bytes are still available in socket (like stream_get_meta_data()['unread_bytes']).
So you need to choose your prefered maximum $length (like 133693415:) or use non-blocking mode (for realy big data reciving).

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t33th4n at gmail dot com ¶

15 years ago


I don't know if is it stated anywhere with this clearance, but here is the source code for detecting the connection abort/closure for sockets testing with socket_read function:



<?php

$buf = @socket_read($routes[$i][$connectionid]['tunnelsrc'], $buffer_size);

if ($buf === '')

{

    $routes[$i][$connectionid]['disconnected']='Conenction abort at source side';

}

?>



($buf === '') is the key :)



I was making an ecrypted tunnel script with mcrypt and was annoying that i could not detect the connection abort from any side.

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Anonymous ¶

17 years ago


On non-blocking connections it may not return full length requested.

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Niels laukens ¶

18 years ago


This paragraph is confusing:

socket_read() returns the data as a string on success, or FALSE on error (including if the remote host has closed the connection). The error code can be retrieved with socket_last_error(). This code may be passed to socket_strerror() to get a textual representation of the error.
Note: socket_read() returns a zero length string ("") when there is no more data to read.

My tests (on PHP 5.1.4) show that when you socket_read() on a shutdown-socket, it returns FALSE when using PHP_NORMAL_READ, but returns "" when reading in PHP_BINARY_READ.

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Bill Kuker ¶

19 years ago


Just a note that on my system the length seems to have an undocumented upper bound of 65536. I was being lazy and not read()ing in a while loop until I pointed it at real data ;)

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schst at php-tools dot de ¶

21 years ago


You may download a generic server class at http://www.php-tools.de
This class will accept the sockets read data from it and hands it to a callback function. Furthermore there are methods for connection handling included.

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-1

tech [{at}] swatcash [{dot}] com ¶

16 years ago


Messed up the end of my previous one. Corrected version here: 

a simple work around to non-blocking working with normal read is like so:

$read = array($socket);
$write  = NULL;
$except = NULL;
while(1) {
    $num_changed_sockets = socket_select($read, $write, $except, 0, 1);
    if ( $num_changed_sockets > '0' ) {
        socket_read($socket,10000,PHP_NORMAL_READ);
    } 
}

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-1

magicking89 at hotmail dot com ¶

21 years ago


if you want to use a non block socket you must to use socket_last_error

if(!socket_last_error($sc)){
   if($buffer=socket_read($sc,512,PHP_NORMAL_READ)){
      echo $buffer;
   }
}

if you use it your script wont take all your memory

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-2

sahel dot nuri at outlook dot com ¶

7 years ago


This little, important fact would save your time.
If you want to recognize that your client is disconnected without any message, you have to select the right flag.
Because, if you use the flag PHP_BINARY_READ:
<?php
function read($sock){
    while($buf = @socket_read($sock, 1024 [, PHP_BINARY_READ ]))
        if($buf = trim($buf))
            break;

    return $buf;
}
?>
and the users disconnects, the function will returns an empty string.
But if you use the flag PHP_NORMAL_READ:
<?php
function read($sock){
    while($buf = @socket_read($sock, 1024, PHP_NORMAL_READ))
        if($buf = trim($buf))
            break;

    return $buf;
}
?>
the function will returns a false.

I hope this will help you. I wasted one hour of my time to solve this problem.

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-4

ein at anti-logic dot com ¶

17 years ago


the proper way to detect a closed connection is to check socket_last_error.

Connection reset by peer is 104 (either use socket_strerror or don't suppress errors for the time being to find these out), sooo.

while($buffer=@socket_read($sock,512,PHP_NORMAL_READ)){
    echo $buffer;
}
if(socket_last_error($sock) == 104) {
    echo "Connection closed";
}

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-3

jgbustos at gmail dot com ¶

17 years ago


PHP on win32 developers, please look at this bug report before using the PHP_NORMAL_READ option:

http://bugs.php.net/bug.php?id=21197

In a nutshell, using PHP_NORMAL_READ will make your calls to socket_read() return an empty buffer every time.

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