socket_read

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

    socket_read — Reads a maximum of length bytes from a socket

    Description

    socket_read(Socket $socket, int $length, int $mode = PHP_BINARY_READ): string|false

    The function socket_read() reads from the Socket instance socket created by the socket_create() or socket_accept() functions.

    Parameters

    socket

    A Socket instance created with socket_create() or socket_accept().

    length

    The maximum number of bytes read is specified by the length parameter. Otherwise you can use \r, \n, or \0 to end reading (depending on the mode parameter, see below).

    mode

    Optional mode parameter is a named constant:

    Return Values

    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.

    Changelog

    Version Description
    8.0.0 socket is a Socket instance now; previously, it was a resource.

    See Also

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    User Contributed Notes 21 notes

    up
    30
    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)
    up
    2
    d dot bergloev at gmail dot com
    4 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.
    up
    2
    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.
    up
    4
    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...
    up
    5
    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.
    up
    3
    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
    ?>
    up
    1
    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.
    up
    1
    Anonymous
    16 years ago
    On non-blocking connections it may not return full length requested.
    up
    0
    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;
    }
    up
    0
    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).
    up
    0
    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.
    up
    0
    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);
    }
    }
    up
    0
    nad0r1 at hush dot ai
    16 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);
    ?>
    up
    0
    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.
    up
    0
    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.
    up
    -1
    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
    $ret==="" : client disconnected for sure
    up
    -1
    sahel dot nuri at outlook dot com
    7 years ago
    This little, important fact would save your time.
    If you want to recognize that your client is disconnected without any message, you have to select the right flag.
    Because, if you use the flag PHP_BINARY_READ:
    <?php
    function read($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.
    up
    -1
    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 ;)
    up
    -2
    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";
    }
    up
    -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
    up
    -4
    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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