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.