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    socket_select

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

    socket_select — Führt einen select()-Systemaufruf auf den gegebenen Socket-Arrays aus, wobei ein Zeitlimit bestimmt wird

    Beschreibung

    socket_select(
        ?array &$read,
        ?array &$write,
        ?array &$except,
        ?int $seconds,
        int $microseconds = 0
    ): int|false

    socket_select() nimmt als Parameter Socket-Arrays entgegen und wartet, ob diese ihren Status ändern. Diejenigen, die Hintergrundwissen über BSD-Sockets haben, werden feststellen, dass diese Socket-Arrays in Wirklichkeit die sogenannten Dateideskriptor-Mengen sind. Drei voneinander unabhängige Arrays mit Sockets werden überwacht.

    Parameter-Liste

    read

    Die Sockets, die im read-Array aufgelistet sind, werden daraufhin überwacht, ob Zeichen zum Auslesen zur Verfügung gestellt werden. (Um genauer zu sein: es wird überwacht, ob ein Lesevorgang nicht blockiert würde - ein Socket ist nämlich auch dann bereit, wenn er bis zum Dateiende gelesen hat. In diesem Fall gibt socket_read() einen leeren String zurück.)

    write

    Die Sockets, die im write-Array aufgelistet sind, werden daraufhin überwacht, ob ein Schreibvorgang nicht blockiert würde.

    except

    Die Sockets, die im except-Array aufgelistet sind, werden auf Ausnahmen überwacht.

    seconds

    seconds und microseconds bilden zusammen den timeout-Parameter. Der timeout ist eine obere Schranke für die Zeit, die verstreichen kann, bis socket_select() zurückkehrt. seconds kann 0 sein, wodurch socket_select() sofort zurückkehrt. Dies ist nützlich beim Polling. Falls der Parameter seconds null ist (kein Timeout), kann socket_select() unendlich lange blockieren.

    microseconds

    Warnung

    Beim Beenden werden alle Arrays aktualisiert, und zeigen an, welche Sockets ihren Status geändert haben.

    Sie brauchen nicht jedes Array einzeln an socket_select() übergeben. Sie können die Arrays auch weglassen und stattdessen leere Arrays oder null angeben. Vergessen Sie nicht, dass diese Arrays per Referenz übergeben werden, und dass sie verändert werden, nachdem die Funktion socket_select() beendet ist.

    Hinweis:

    Wegen einer Einschränkung in der aktuellen Zend Engine ist es nicht möglich, eine Konstante, wie etwa null, direkt als Parameter an Funktionen zu übergeben, die ihre Argumente als Referenzen erwarten. Statt dessen kann eine temporäre Variable oder eine Ausdruck, in dem der am weitesten links stehende Teilausdruck eine temporäre Variable ist, verwendet werden.

    Beispiel #1 null mit socket_select() benutzen:

    <?php
    $e     = NULL;
    socket_select($r, $w, $e, 0);
    ?>

    Rückgabewerte

    Bei Erfolg gibt socket_select() die Anzahl der Sockets zurück, die in den aktualisierten Arrays enthalten sind. Falls der Timeout wirksam wird, bevor irgend etwas Interessantes passiert, ist das Funktionsergebnis 0. Falls ein Fehler auftritt, wird false zurückgegeben. Der Fehlercode kann dann mit socket_last_error() abgefragt werden.

    Hinweis:

    Wenn ein Fehler aufgespürt werden soll, muss unbedingt der Operator === benutzt werden. Weil socket_select() auch 0 zurückgeben kann, wird der Vergleich mit == sonst zu true ausgewertet.

    Beispiel #2 Rückgaben von socket_select() verstehen

    <?php
    $e     = NULL;
    if (    false === socket_select($r, $w, $e, 0)) {
    echo     "socket_select() fehlgeschlagen, Grund: " .
    socket_strerror(socket_last_error()) . "\n";
    }
    ?>

    Beispiele

    Beispiel #3 socket_select()-Beispiel

    <?php
    /* Das Array read vorbereiten */
    $read = array($socket1, $socket2);
    $write = NULL;
    $except = NULL;
    $num_changed_sockets = socket_select($read, $write, $except, 0);

    if (    $num_changed_sockets === false) {
    /* Fehlerbehandlung */
    } else if ($num_changed_sockets > 0) {
    /* Mindestens an einem Socket ist etwas Interessantes passiert */
    }
    ?>

    Anmerkungen

    Hinweis:

    Seien Sie sich bewusst, dass manche Socket-Implementierungen sehr sorgfältig benutzt werden müssen. Ein paar grundsätzliche Regeln:

    • Sie sollten immer versuchen, socket_select() ohne Timeout zu benutzen. Ihr Programm sollte nichts zu tun haben, wenn keine Daten verfügbar sind. Code, der von Zeitbegrenzungen abhängig ist, ist normalerweise nicht portierbar und schwierig zu debuggen.
    • Es darf kein Socket in die Arrays eingefügt werden, wenn Sie nicht vorhaben, die Ergebnisse nach der Ausführung von socket_select() zu prüfen und entsprechend darauf zu reagieren. Nachdem socket_select() beendet ist, müssen alle Sockets in allen Socket-Arrays geprüft werden. Jeder Socket, der zum Schreiben zur Verfügung steht, muss beschrieben werden und aus jedem Socket, der zum Lesen verfügbar ist, muss gelesen werden.
    • Bei Schreib-/Leseoperationen auf den Sockets in den Arrays muss damit gerechnnet werden, dass nicht notwendigerweise alle Daten geschrieben/gelesen werden, die angeben wurden. Seien Sie darauf vorbereitet, dass Sie möglicherweise nur ein einziges Byte schreiben/lesen können.
    • Fast allen Socket-Implementierungen ist gemeinsam, dass sie nur eine einzige Ausnahme in dem Array except auffangen können. Und zwar, wenn bandexterne Daten von einem Socket empfangen werden.

    Siehe auch

    add a note add a note

    User Contributed Notes 23 notes

    up
    48
    vardhan ( at ) rogers ( dot ) com
    19 years ago
    A simple PHP script using socket_select() to manage multiple connections.
    connect using "telnet localhost 9050". it broadcasts your messages that you send through telnet to other users connected to the server -- sort of like a chat script

    #!/usr/local/bin/php
    <?php

        $port     = 9050;
       
            // create a streaming socket, of type TCP/IP
            $sock = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
       
            // set the option to reuse the port
            socket_set_option($sock, SOL_SOCKET, SO_REUSEADDR, 1);
       
            // "bind" the socket to the address to "localhost", on port $port
        // so this means that all connections on this port are now our resposibility to send/recv data, disconnect, etc..
            socket_bind($sock, 0, $port);
       
            // start listen for connections
            socket_listen($sock);

            // create a list of all the clients that will be connected to us..
        // add the listening socket to this list
            $clients = array($sock);
       
        while (    true) {
                // create a copy, so $clients doesn't get modified by socket_select()
                $read = $clients;
           
                // get a list of all the clients that have data to be read from
            // if there are no clients with data, go to next iteration
                if (socket_select($read, $write = NULL, $except = NULL, 0) < 1)
                continue;
           
                // check if there is a client trying to connect
                if (in_array($sock, $read)) {
                    // accept the client, and add him to the $clients array
                    $clients[] = $newsock = socket_accept($sock);
               
                    // send the client a welcome message
                    socket_write($newsock, "no noobs, but ill make an exception :)\n".
                    "There are ".(count($clients) - 1)." client(s) connected to the server\n");
               
                    socket_getpeername($newsock, $ip);
                echo     "New client connected: {$ip}\n";
               
                    // remove the listening socket from the clients-with-data array
                    $key = array_search($sock, $read);
                unset(    $read[$key]);
            }
           
                // loop through all the clients that have data to read from
                foreach ($read as $read_sock) {
                    // read until newline or 1024 bytes
                // socket_read while show errors when the client is disconnected, so silence the error messages
                    $data = @socket_read($read_sock, 1024, PHP_NORMAL_READ);
               
                    // check if the client is disconnected
                    if ($data === false) {
                        // remove client for $clients array
                        $key = array_search($read_sock, $clients);
                    unset(    $clients[$key]);
                    echo     "client disconnected.\n";
                        // continue to the next client to read from, if any
                        continue;
                }
               
                    // trim off the trailing/beginning white spaces
                    $data = trim($data);
               
                    // check if there is any data after trimming off the spaces
                    if (!empty($data)) {
               
                        // send this to all the clients in the $clients array (except the first one, which is a listening socket)
                        foreach ($clients as $send_sock) {
                   
                            // if its the listening sock or the client that we got the message from, go to the next one in the list
                            if ($send_sock == $sock || $send_sock == $read_sock)
                            continue;
                       
                            // write the message to the client -- add a newline character to the end of the message
                            socket_write($send_sock, $data."\n");
                       
                    }     // end of broadcast foreach
                   
                    }
               
            }     // end of reading foreach
            }

            // close the listening socket
            socket_close($sock);
    ?>
    up
    4
    malcolm.murphy
    8 years ago
    This was mentioned by [Viorel] above but I think it warrants being repeated...

    The example provided by [vardhan ( at ) rogers ( dot ) com], while otherwise exceptional, uses the value int(0) for $tv_sec which will cause the iteration to loop as fast as possible, consequently using up any available CPU time.

    *** Ideally, $tv_sec should always be set to NULL ***, especially if you are using socket_select in a loop. If you must temporarily stop listening for events to perform another task, then the timeout should be as high as possible to reduce CPU strain (another note suggested preventing 100% CPU usage by setting a low $tv_usec value, which only makes the problem slightly less worse but does not solve it).

    Setting the timeout to an explicit null value is basically the same as setting it to infinite. The script will only execute the while loop once every time there is an event.
    up
    3
    antti r
    8 years ago
    as of 12/2015 and php 5.3.3, the socket_select() maximum sockets is still 1024 and not risable by process file limits (bash ulimit -n). PHP new compilation is required to raise the limits. Or one might rather choose forking or multiple binaries.
    up
    3
    John
    14 years ago
    The way the document describes socket_select()'s handling of sockets polled for read is rather obscure.

    It says that it checks to see if reading would not "block," but the overall description of socket_select() says it checks for a change in blocking status. Unfortunately, these are in conflict.

    If a socket already has data in the buffer, calling socket_select() on that socket would never return (assuming null timeout), and would block forever. :-( This is because the blocking status wouldn't change. It simply stays "non-blocking"

    It is important to remember NOT to select() on a socket which may already have data available.

    An example...
    <?php
    //... $socket is already here...
    $done = false;
    $n = 0;
    do{
            $tmp = 0;
            $r = $w = $e = array();
            $r = array($socket);
            socket_select($r,$w,$e,null);
            $n = socket_recv($socket, $tmp, 1024, 0);

            //$done = true; //Something determines that we are done reading...
    }while(!$done);
    ?>
    This MAY NOT work... socket_select() is always being called... but we may have data in the input buffer.

    We need to ensure that the last time we read, nothing was read... (empty buffer)
    <?php
    //... $socket is already here...
    $done = false;
    $n = 0;
    do{
            $tmp = 0;
            $r = $w = $e = array();
            $r = array($socket);
        if(    $n === 0) socket_select($r,$w,$e,null);
            $n = socket_recv($socket, $tmp, 1024, 0);

            //$done = true; //Something determines that we are done reading...
    }while(!$done);
    ?>
    up
    1
    Richard Neill
    20 years ago
    It is probably a bad idea to watch an array of sockets for input with socket_select, and then socket_read() using PHP_NORMAL_READ.

    Although this seems desirable, you can end up with a permanently blocked program, if someone sends you malformed input which is missing a trailing \n \r. Guess how I found that out.
    up
    1
    calimero dot NOSPAM at NOSPAM dot creatixnet dot com
    21 years ago
    Please note that the timeout parameter has important side-effects on the CPU usage of your script.

    Setting the timeout to 0 will make your CPU looping without any time to have some rest and handle other running processes on your system, causing the system load to increase heavily while your script is running.

    Personnaly, I use a value of 15 ms for this parameter. this ensures a good listening frequency while letting your system load clear.

    Example :
    $read = array($ListeningSocket);
    $num_changed_sockets = socket_select($read, $write = NULL, $except = NULL, 0, 10);

    Hope this helps.
    up
    1
    qartis at gmail dot com
    16 years ago
    In regards to the code posted by vardhan ( at ) rogers ( dot ) com, it appears that on the following line:
            if (socket_select($read, $write = NULL, $except = NULL, 0) < 1)
    the timeout parameter is accidentally set to 0, rather than NULL. This means that the select call will return immediately rather than blocking indefinitely.

    Change the socket_select line to the following for great success:
            if (socket_select($read, $write = NULL, $except = NULL, NULL) < 1)
    up
    2
    Viorel
    11 years ago
    Probably you will want to use

    // get a list of all the clients that have data to be read from
    // if there are no clients with data, go to next iteration
            if (socket_select($read, $write = NULL, $except = NULL, NULL) < 1)
                continue;
               
    instead 
            if (socket_select($read, $write = NULL, $except = NULL, 0) < 1)
                continue;
    which will hang your CPU to 100% (return immediate if nothing to be done)
    up
    0
    juanfe0245 at gmail dot com
    4 years ago
    <?php
    //Creamos un socket de transmisión de tipo TCP / IP.
    $servidorSocket=socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
    //Configuramos la opción para reutilizar el puerto.
    socket_set_option($servidorSocket,SOL_SOCKET,SO_REUSEADDR,1);
    /*
        Vinculamos el socket a nuestro puerto y dirección IP.
        Ahora, todas las conecciones en este puerto son nuestro responsabilidad para recibir y enviar datos.
    */
    socket_bind($servidorSocket,'localhost',9000);
    //Comenzamos a escuchar conexiones.
    socket_listen($servidorSocket);
    /*
        Creamos un arreglo con todos los clientes que se conectarán a nuestro servidor.
        Añadimos nuestro socket servidor al arreglo de clientes.
    */
    $clientes=[$servidorSocket];
    $null=null;
    while(    true){
            //Creamos una copia de $clientes, debido a que $clientes no se modifica por la función socket_select().
            $nuevoClienteLector=$clientes;
            //Obtenemos una lista de todos los clientes que tienen datos para leer.
            socket_select($nuevoClienteLector,$null,$null,10);
            //Verificamos si hay un cliente tratando de conectarse.
            if(in_array($servidorSocket,$nuevoClienteLector)){
                //Aceptamos el cliente y lo añadimos al arreglo de $clientes.
                $nuevoCliente=socket_accept($servidorSocket);
            echo     "Socket aceptado.\n";
                $clientes[]=$nuevoCliente;
                //Obtenemos el encabezado del cliente y realizamos la comprobación del handshake.
                $encabezado=socket_read($nuevoCliente,1024);
                handshake($nuevoCliente,$encabezado);
                //Eliminamos el cliente del arreglo $nuevoClienteLector.
                $nuevoClienteIndex=array_search($servidorSocket,$nuevoClienteLector);
            unset(    $nuevoClienteLector[$nuevoClienteIndex]);
        }
            //Recorremos todos los clientes que tienen datos por leer.
            foreach($nuevoClienteLector as $cliente){
                //Recibimos información del cliente conectado.
                while(socket_recv($cliente,$datosCliente,1024,0)>=1){
                    //Decodificamos el mensaje que viene en bytes.
                    $mensaje=decodificar($datosCliente);
                    //Enviamos el mensaje a todos los sockets conectados.
                    enviar($clientes,$mensaje);
                echo     $mensaje."\n";
                break     2;
            }
                //Verificamos si el cliente esta desconectado.
                $datosCliente=@socket_read($cliente,1024,PHP_NORMAL_READ);
            if(    $datosCliente===false){
                    $clienteIndex=array_search($cliente,$clientes);
                    //Eliminamos el cliente del arreglo $clientes.
                    unset($clientes[$clienteIndex]);
                echo     "Cliente desconectado.\n";
            }
        }
    }
    function     enviar($clientes,$mensaje){
            $mensaje=codificar($mensaje);
        foreach(    $clientes as $cliente){
            @    socket_write($cliente,$mensaje,strlen($mensaje));
        }
    }
    socket_close($servidorSocket);
    function     codificar($socketData){
            $b1 = 0x80 | (0x1 & 0x0f);
            $length = strlen($socketData);
       
        if(    $length <= 125)
                $header = pack('CC', $b1, $length);
        elseif(    $length > 125 && $length < 65536)
                $header = pack('CCn', $b1, 126, $length);
        elseif(    $length >= 65536)
                $header = pack('CCNN', $b1, 127, $length);
        return     $header.$socketData;
    }
    function     decodificar($socketData) {
            $length = ord($socketData[1]) & 127;
        if(    $length == 126) {
                $masks = substr($socketData, 4, 4);
                $data = substr($socketData, 8);
        }
        elseif(    $length == 127) {
                $masks = substr($socketData, 10, 4);
                $data = substr($socketData, 14);
        }
        else {
                $masks = substr($socketData, 2, 4);
                $data = substr($socketData, 6);
        }
            $socketData = "";
        for (    $i = 0; $i < strlen($data); ++$i) {
                $socketData .= $data[$i] ^ $masks[$i%4];
        }
        return     $socketData;
    }
    function     handshake($client_socket_resource,$received_header) {
            $headers = array();
            $lines = preg_split("/\r\n/", $received_header);
        foreach(    $lines as $line){
                $line = chop($line);
            if(    preg_match('/\A(\S+): (.*)\z/', $line, $matches)) $headers[$matches[1]] = $matches[2];
        }
            $secKey = $headers['Sec-WebSocket-Key'];
            $secAccept = base64_encode(pack('H*', sha1($secKey . '258EAFA5-E914-47DA-95CA-C5AB0DC85B11')));
            $buffer  = "HTTP/1.1 101 Web Socket Protocol Handshake\r\n" .
            "Upgrade: websocket\r\n" .
            "Connection: Upgrade\r\n" .
            "Sec-WebSocket-Accept:$secAccept\r\n\r\n";
            socket_write($client_socket_resource,$buffer,strlen($buffer));
    }
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    0
    renmengyang567 at gmail dot com
    5 years ago
    <explain>
    A simple socket-select case ^_^

    <?php
    $sock     = socket_create(AF_INET, SOCK_STREAM, getprotobyname('tcp'));
    socket_set_option($sock, SOL_SOCKET, SO_REUSEADDR, 1);
    socket_bind($sock, '127.0.0.1',5000);
    socket_listen($sock,1024);
    $all_sock[(int)$sock] = $sock;

    while (    true) {
            $read = $write = $except = [];
            $tv_sec = 5;
            $tv_usec = 5000;
            $read = $all_sock;
       
            $changed = socket_select($read, $write, $except, $tv_sec, $tv_sec);

        if (    false == $changed)
            print     "[error]socket_select() failed
            ("     .socket_strerror(socket_last_error()) . ")\n";

        if (    $changed < 1)
           continue;

            //var_dump($read);
        //sleep(2);
            foreach ($read as $rsock) {
                // 服务端连接
                if ($rsock === $sock) {
                    $client = socket_accept($sock);
                    $all_sock[(int)$client] = $client;
           
            } else {    //客户端连接
                    $msg= socket_read($rsock, 400,PHP_NORMAL_READ);
                if (    $msg !== '') {
                        var_dump($msg);
                }
            }
        }
    }
    socket_close($sock);
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    2
    magemerlin at list dot ru
    14 years ago
    If you using a Flash client - you should know some specific features:

    1) when client connects to the server - it is sending to you "<policy-file-request/>"."\0" string. Server should answer an XML policy file, then disconnect from this client. Code is something like

    if ('<policy-file-request/>'==substr($data, 0, 22))
                    {
                        echo "policy requset.\n";
                        flush();ob_flush();
                        $msg = '<'.'?xml version="1.0"?>
    <!DOCTYPE cross-domain-policy SYSTEM "http://www.macromedia.com/xml/dtds/cross-domain-policy.dtd">
    <cross-domain-policy>
    <allow-access-from domain="*" to-ports="*" />
    </cross-domain-policy>'."\0";
                        echo "Say to client (crossdomain.xml) ... ";
                        flush();ob_flush();
                        socket_write($read_sock, $msg, strlen($msg));
                        echo "OK\n";
                        flush();ob_flush();
                       
                        echo "Closing ... ";
                        flush();ob_flush();
                        socket_close($read_sock);
                        echo "OK\n";
                        flush();ob_flush();
                    }
                    else
                    {
    // here is normal IO operations with client
    }

    2) every output to client should be ended with "\0" (if using XMLSocket in Flash client) - otherwise flash will not generate onData event

    Russian examples is there - http://www.flasher.ru/forum/showpost.php?p=901346&postcount=7
    up
    0
    simon dot riget at gmail dot com
    10 years ago
    A verry simple HTTP webserver written in PHP
    Run it in the shell with php <name of file> and test in in the browser with <server address>:8080/test

    <?php
          // Reduce the amount of warnings displayed
          error_reporting(E_ALL ^ E_NOTICE);

          // Set up socket for listening
          $host_socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
      if(!    $host_socket) die("Failed to start event server. socket_create: ". socket_strerror(socket_last_error())."\n");

          // set the option to reuse the port
          if(! socket_set_option($host_socket, SOL_SOCKET, SO_REUSEADDR, 1) )
        die(    "Failed to start event server. socket_set_option: ". socket_strerror(socket_last_error())."\n");

          // bind host socket to localhost or 0.0.0.0 on port 8080
          if(! socket_bind($host_socket,"0.0.0.0",8080) )
        die(    "Failed to start event server. socket_bind: ". socket_strerror(socket_last_error())."\n");

          // start listening for connections
          if(! socket_listen($host_socket,10) )
        die(    "Failed to start event server. socket_listen: ".socket_strerror(socket_last_error())."\n");

      while (    true) {
            // Make list of sockets to listen for changes in, including host
            $read = array($host_socket);
            
            // get a list of all the clients that have data to be read from
            $ready=@socket_select($read, $write = NULL, $except = NULL,0);
        if (    $ready=== false)
          die(    "Failed to listen for clients: ". socket_strerror(socket_last_error()));

            // a client request service
            elseif($ready>0){
              // accept new client
              $newsocket = socket_accept($host_socket);

              // Read from socket
              $input = socket_read($newsocket, 1024);
          if(    $input){
            unset(    $client_header);
                // Read headers; Split into safe lines
                $line=explode("\n",preg_replace('/[^A-Za-z0-9\-+\n :;=%*?.,\/_]/','',substr($input,0,2000)));
                // Split request line into its parts
                list($client_header["method"],$client_header["url"],$client_header["protocol"])=explode(" ",$line[0]);
                // Remove the request line again.
                unset($line[0]);
                // Make key=value array of headers
                foreach($line as $l){
              list(    $key,$val)=explode(": ",$l);
              if(    $key) $client_header[strtolower($key)]=$val;
            }
                // Get IP of client
                socket_getpeername($newsocket, $client_header['ip']);

                // Decode url
                $client_header+=(array)parse_url($client_header['url']);
                parse_str($client_header['query'],$client_header['arg']);

                print_r($client_header);

                // Serve file
                if(strpos($client_header['path'],".html") && file_exists(__DIR__.$client_header['path'])){
              echo     "Sending a HTML page to client\n";
                  socket_write($newsocket,"$client_header[protocol] 200 OK\r\n");   
                  socket_write($newsocket,"Content-type: text/html; charset=utf-8\r\n\r\n");
                  socket_write($newsocket,file_get_contents(__DIR__.$client_header['path'])."\r\n\r\n");
                  socket_close($newsocket);
            }elseif(    $client_header['path']=="/test"){
              echo     "Sending test HTML page to client\n";
                  socket_write($newsocket,"<!DOCTYPE HTML><html><head><html><body><h1>Its working!</h1>Have fun\r\n");
                  socket_write($newsocket,"<pre>Request header: ". print_r($client_header,true) . "</pre>\r\n");
                  socket_write($newsocket,"</body></html>\r\n\r\n");
                  socket_close($newsocket);
            }else{
              echo     "$client_header[protocol] 404 Not Found\r\n";
                  socket_write($newsocket,"$client_header[protocol] 404 Not Found\r\n\r\n");  
                  socket_close($newsocket);
            }
          }
        }
      }
          socket_close($host_socket);
    ?>
    up
    0
    jean at briskula dot si
    13 years ago
    As it was already said, some clients need \0 character to end transmission, for example Flash's XMLSocket.

    You should also be prepared to read less data than you have requested.

    Here is an example of a socket buffer - it's an array which has socket resources for keys and an array of a timestamp and recieved data as values.

    I find that the best practice for sending data is trailing it with a new line and zero character (\n\0), because you will probably have different types of clients which behave differently for reading data from sockets. Some need a \n to fire an event, some need \0.

    For recieving data, sometimes you will get splitted data - this can hapen because the buffer is full (in my example 8192 bytes) or it just gets broken during transmission in lower levels.

    Sometimes you can read two messages at once, but they have a zero character in between, so you can just use preg_split() to split the messages. The second message may not be complete, so you add it to your buffer.

    <?php
            const message_delimiter = "\n\0";

            /*
         * Clear socket buffers older than 1 hour
         */
            function clear_buffer() {
            foreach(    $this->buffer as $key=>$val) {
                if(    time() - $val['ts'] > 3600) {
                    unset(    $this->buffer[$key]);
                }
            }
        }

            /*
         * Add data to a buffer
         */
            function buffer_add($sock,$data) {
            if(!isset(    $this->buffer[$sock])) {
                    $this->buffer[$sock]['data'] = '';
            }

                $this->buffer[$sock]['data'] .= $data;
                $this->buffer[$sock]['ts'] = time();
        }

        function     buffer_get($sock) {
                // split buffer by the end of string
                $lines = preg_split('/\0/',$this->buffer[$sock]['data']);

                // reset buffer to the last line of input
            // if the buffer was sent completely, the last line of input should be
            // an empty string
                $this->buffer[$sock]['data'] = trim($lines[count($lines)-1]);

            if(!empty(    $this->buffer[$sock]['data'])) {
                    debug("buffer is not empty for $sock, len: ".strlen($this->buffer[$sock]['data']));
            }

                // remove the last line of input (incomplete data)
            // parse any complete data
                unset($lines[count($lines)-1]);

                // return only the fully sent data
                return $lines;
        }

        function     read(&$sock,$len=8192,$flag=MSG_DONTWAIT) {
                $lines = array();

                $this->clear_buffer();

                $bytes_read = @socket_recv($sock,$read_data,$len,$flag);

            if (    $bytes_read === false || $bytes_read == 0) {
                return     false;
            } else {
                    debug("recv: $read_data");
                    $this->buffer_add($sock,$read_data);
                return     $this->buffer_get($sock);
            }
        }

            /*
         * Write to a socket
         * add a newline and null character at the end
         * some clients don't read until new line is recieved
         *
         * try to send the rest of the data if it gets truncated
         */
            function write(&$sock,$msg) {
                $msg = $msg.self::message_delimiter;
                $length = strlen($msg);
            while(    true) {
                    $sent = @socket_write($sock,$msg,$length);
                if(    $sent <= 0) {
                    return     false;
                }
                if(    $sent < $length) {
                        $msg = substr($msg, $sent);
                        $length -= $sent;
                        debug("Message truncated: Resending: $msg");
                } else {
                    return     true;
                }
            }
            return     false;
        }
    ?>
    up
    0
    eidberger at jakota dot de
    15 years ago
    Just noticed that you have to loop socket_select () when using UDP to get all queued packets:

    <?php
    while (socket_select ($aRead, $aWrite, $aExcept, 1) > 0) {
        foreach (    $aReadUdp as $oSocket) {
                $this->clientReadUdp ($oSocket);
        }
    }
    ?>

    That's important because every call of socket_select () on UDP brings you only one result. But there could be 10.000 results queued and if your turnarround time is to slow (server busy, other sleeps etc.), you'll never progress all results in near realtime.
    up
    0
    danny at dansheps dot com
    16 years ago
    Just to add to this.  Since the information contained in the notes is somewhat old.   It appears keys are being preserved now.

    So, if you rely on knowing which keys need to be worked with and were like me and thought that it didnot preserve.  Well it does.
    up
    0
    Anonymous
    17 years ago
    If you want to use a simple fractional value for timeout:

    <?php
    socket_select    (..., floor($timeout), ceil($timeout*1000000));
    ?>
    up
    1
    julian dot haupt at gmx dot de
    22 years ago
    hello,
    i just made a class which acts similiar to Perl's IO::Select in order to make socket selecting very easy

    your script should look something like that:

    <?php
    $server     = new Server;
    $client = new Client;

    for (;;) {
      foreach (    $select->can_read(0) as $socket) {

        if (    $socket == $client->socket) {
              // New Client Socket
              $select->add(socket_accept($client->socket));
        }
        else {
              //there's something to read on $socket
            }
      }
    }
    ?>

    you should of course implement some routines to detect broken sockets and remove them from the select object.

    you can also do output buffering and check in the main-loop for sockets that are ready to write

    <?php
    class select {
      var     $sockets;

      function     select($sockets) {

            $this->sockets = array();

        foreach (    $sockets as $socket) {
              $this->add($socket);
        }
      }

      function     add($add_socket) {
            array_push($this->sockets,$add_socket);
      }

      function     remove($remove_socket) {
            $sockets = array();

        foreach (    $this->sockets as $socket) {
          if(    $remove_socket != $socket)
                $sockets[] = $socket;
        }

            $this->sockets = $sockets;
      }

      function     can_read($timeout) {
            $read = $this->sockets;
            socket_select($read,$write = NULL,$except = NULL,$timeout);
        return     $read;
      }

      function     can_write($timeout) {
            $write = $this->sockets;
            socket_select($read = NULL,$write,$except = NULL,$timeout);
        return     $write;
      }
    }
    ?>
    up
    0
    Whosawhatsis at that google email thingy
    18 years ago
    Another solution to the problem of keys not being preserved is to have an additional array for looking up sockets that uses their resource identifiers as keys. This can be obtained using array_flip() in some cases, but is particularly useful if each socket is associated with an object. In this case, you can make the object's constructor add a pointer to itself to the lookup array with its socket resource identifier as a key and use the following code to execute a read method for the object associated with each socket returned by socket_select():

    <?php
    socket_select    ($reads, $writes, $excepts, 0);

    foreach (    $sockets as $socket) {
            $lookuparray[$socket]->read();
    }
    ?>
    up
    0
    crimson at NOSPAMtechnologist dot com
    19 years ago
    Note that the resulting arrays do NOT maintain keys (PHP 4.3.2) after being run through this function:

    Before:
    Array
    (
        [Client_Socket] => Resource id #6
        [Server_Socket] => Resource id #9
    )

    After:
    Array
    (
        [0] => Resource id #6
        [1] => Resource id #9
    )

    It would have been nice to have the keys stay to figure out which stream you need to receive from, but you'll have to use some fancy foreach loop to figure out which sockets to check.
    up
    -1
    ludvig dot ericson at gmail dot com
    19 years ago
    Regarding the comment below, No, it does not, it's a system call and I believe it's rather hard to preserve keys.

    Additionally, socket_select should be used like it was a user-inputted array, that you don't know what you sent in to.

    <?php
    $reads     = $clients;
    $reads[] = $server;

    socket_select($reads);

    foreach (    $reads as $read) {
            /* do some stuff */
    }
    ?>
    up
    -1
    drenintell
    19 years ago
    The continuation of my my previous post on 28-Apr-2005 10:19 at
    http://ca3.php.net/manual/en/function.socket-select.php

    Here it is: (Link is broken into 2 parts)

    'http://gtkphp.org/php_socket_select_hangs
    _explanation_and_solution.html'
    up
    -3
    daveb at optusnet dot com dot au
    22 years ago
    If you haven't done any network programming before, PHP's socket_select() might appear a bit strange to you. I've written a simple php "partyline" script to demonstrate the multi-socket use of select'ing at http://dave.dapond.com/socketselect.php.txt
    up
    -10
    Aaron (aaron at acephalo dot us)
    15 years ago
    socket_select() can also serve as a more granular sleep():

    <?php
          # half-second sleep
          $undef = array();
          socket_select($undef, $undef, $undef, 0, "500000");
    ?>
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