Bug #81304 [Nab]: simple socket listen and receive scripts transfer incomplete data

Edit report at https://bugs.php.net/bug.php?id=81304&edit=1 ID: 81304 User updated by: odarcan at gmail dot com Reported by: odarcan at gmail dot com Summary: simple socket listen and receive scripts transfer incomplete data Status: Not a bug Type: Bug Package: Sockets related Operating System: linux PHP Version: 7.4.21 Block user comment: N Private report: N New Comment: I dont see how tcp can send incomplete data and this is accepted as normal, I really how someone can explain or point me in the right direction, nothing is mentioned about this in the php manuals or any inclination on how do replicate or overcome such a phenomenon or that it is something common, nor that it is even something commonly known. that tcp randomly transfers less bytes goes against everything I have learned about tcp. please explain or tell me what this phenomena is called and where in literature it can even be found. if it is not a php issue or maybe a bug in some other system or the many pcs Ive tried it on that would be also acceptable thanks I am awaiting a relevant reply. Previous Comments: ------------------------------------------------------------------------ [2021-07-29 01:22:46] requinix@php.net Please note that the term "buffer overrun" means something very different from what you meant. https://www.php.net/manual/en/function.socket-write.php > Note: > socket_write() does not necessarily write all bytes from the given buffer. > It's valid that, depending on the network buffers etc., only a certain amount > of data, even one byte, is written though your buffer is greater. You have to > watch out so you don't unintentionally forget to transmit the rest of your > data. ------------------------------------------------------------------------ [2021-07-29 00:58:35] odarcan at gmail dot com solution is this apparently socket_write causes buffer overrun when the msg is too big, so send it in chunks instead $l1=strlen($msg); $totaltransferred=0; $bsize=10000; for ($a=0;$a<$l1;$a+=$bsize){ $part=substr($msg,$a,$bsize); $l2=socket_write($msgsocket,$part,strlen($part)); $totaltransferred+=$l2; } if ($totaltransferred<$l1){ o("incomplete transfer"); } ------------------------------------------------------------------------ [2021-07-28 01:14:35] requinix@php.net Sorry, but your problem does not imply a bug in PHP itself. For a list of more appropriate places to ask for help using PHP, please visit http://www.php.net/support.php as this bug system is not the appropriate forum for asking support questions. Due to the volume of reports we can not explain in detail here why your report is not a bug. The support channels will be able to provide an explanation for you. Thank you for your interest in PHP. ------------------------------------------------------------------------ [2021-07-28 01:00:53] odarcan at gmail dot com you can add if (unserialize($r)===false){ echo "incomplete data transfer\n"; } to the line under $r=sendclosetcp(.... to warn that the data sent is incomplete. ------------------------------------------------------------------------ [2021-07-28 00:48:54] odarcan at gmail dot com Description: ------------ a simple tcp socket listen loop (1listen.php) that sends 12mb data to whoever connects to port 1234 and writes "cmd" the receiver script connects to localhost:1234 and writes "cmd" and counts the number of bytes received (2receive.php) receives different amount and rarely, but sometimes the correct amount. 1listen.php <?php ini_set('error_reporting', E_ALL ^ E_NOTICE); ini_set('display_errors', 1); set_time_limit (0); $address = '0.0.0.0'; $port = 1234; function o($t,$x="\n"){ //just placebo for echo echo "s_l: $t$x"; } while (1){ $linger = array ('l_linger' => 0, 'l_onoff' => 1); $socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP); socket_set_option($socket, SOL_SOCKET, SO_LINGER, $linger); $r=socket_bind($socket, $address, $port); if ($r==false){ var_dump($socket); o("Could not bind to address: $address $port"); o("sleeping..."); unset($socket); sleep(1); continue; } $r=socket_listen($socket); if ($r==false){ o("could not listen to socket on $port"); sleep(5); continue; } o("Listening on $address:$port..."); $c=0; while (true){ $msgsocket = socket_accept($socket); socket_set_option($msgsocket, SOL_SOCKET, SO_LINGER, $linger); $received= socket_read($msgsocket,2048,PHP_BINARY_READ); if($received ===false){ echo "socket read error: ".socket_strerror(socket_last_error($msgsock)) . "\n"; sleep(4); continue 2; } o("-----------------------"); if ($received !==""){ $string=trim($received); echo "received: [$string]\n"; $cmd=explode(" ",$string); if ($cmd[0]=="cmd"){ $domain=$cmd[1]; $md5=$cmd[2]; $arr=[]; $n=1; for($a=0;$a<1000;$a++){ for($b=0;$b<1000;$b++){ $arr[$a][$b]=$a;//generate data to send } } $r2=serialize($arr); $l1=strlen($r2); $l2=socket_write($msgsocket,$r2); if ($l2<$l1){ o("incomplete transfer"); } o("wrote $l1 / $l2 bytes"); if ($l2===false){ o("error failure"); } } } socket_close($msgsocket); } socket_close($socket); } shutdown(); ?> 2receive.php <?php $m="cmd"; $r=sendclosetcp("localhost",1234,$m); echo strlen($r); echo "\n"; function o($t,$x="\n"){ global $domain; $computer=""; echo $computer." $t$x"; } function sendclosetcp($ip,$port,$msg){ $clnt_sock = socket_create(AF_INET, SOCK_STREAM, getprotobyname('tcp')); $r=socket_connect($clnt_sock, $ip, $port); if ($r==false){ o("could not connect to $ip $port"); return ""; } socket_write($clnt_sock,$msg); $ret=""; while(1){ $buf=@socket_read($clnt_sock, 10000, PHP_BINARY_READ); if (strlen($buf)<19) var_dump($buf); $ret.=$buf; $e=socket_last_error($clnt_sock); if ($buf===false){ o("1 remote host closed the connection $e"); break; } if ($buf==false){ o("2 remote host closed the connection $e"); break; } if ($buf==""){ o("3 remote host closed the connection $e"); break; } if ($buf===""){ o("4 remote host closed the connection $e"); break; } } o("received ".strlen($ret)." bytes"); return $ret; } ?> Test script: --------------- run 1listen.php in one terminal window and 2receive.php in another each time you run 2receive.php it receives different amount of bytes before the connection is closed, I have tried on more than one computer Expected result: ---------------- "sent x bytes" and "received x bytes" should be the same number seemingly randomly for files over a few mbs, the received amount varies and data transfers are incomplete Actual result: -------------- 1listen.php: wrote 11794899 / 11794899 bytes for example 2receive.php: received 11053512 bytes received 8039296 bytes received 9108280 bytes etc. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=81304&edit=1