Looping The Loop - PHP

You can also write a server that allows for more than just one transaction at a time. Consider the following variant of the first example:

<?
// don't timeout
set_time_limit (0);
// set some variables
$host = "192.168.1.99";
$port = 1234;
// create socket
$socket = socket_create(AF_INET, SOCK_STREAM, 0) or die("Could not create
socket\n");
// bind socket to port
$result = socket_bind($socket, $host, $port) or die("Could not bind to
socket\n");
// start listening for connections
$result = socket_listen($socket, 3) or die("Could not set up socket
listener\n");
echo "Waiting for connections...\n";
// accept incoming connections
// spawn another socket to handle communication
$spawn = socket_accept($socket) or die("Could not accept incoming
connection\n");
echo "Received connection request\n";
// write a welcome message to the client
$welcome = "Roll up, roll up, to the greatest show on earth!\n? ";
socket_write($spawn, $welcome, strlen ($welcome)) or die("Could not send
connect string\n");
// keep looping and looking for client input
do
{
// read client input
$input = socket_read($spawn, 1024, 1) or die("Could not read input\n");
if (trim($input) != "")
{
echo "Received input: $input\n";
// if client requests session end
if (trim($input) == "END")
{
// close the child socket
// break out of loop
socket_close($spawn);
break;
}
// otherwise...
else
{
// reverse client input and send back
$output = strrev($input) . "\n";
socket_write($spawn, $output . "? ", strlen (($output)+2)) or die("Could
not write output\n");
echo "Sent output: " . trim($output) . "\n";
}
}
} while (true);
// close primary socket
socket_close($socket);
echo "Socket terminated\n";
?>

This is almost exactly the same code as that used in the very first example, with the obvious addition of debug messages and a "do-while" loop which allows the server to keep reading new data transmitted by the client, and responding to it. The loop is terminated when the client sends the special session terminator string "END".

Here's the output of a sample session:

$ telnet 192.168.1.99 1234
Trying 192.168.1.99...
Connected to medusa.
Escape character is '^]'.
Roll up, roll up, to the greatest show on earth!
? Look Ma...all backwards
sdrawkcab lla...aM kooL
? jack frost
tsorf kcaj
? END
Connection closed by foreign host.

And here are the corresponding debug messages generated on the server:

$ /usr/local/bin/php -q server.php
Waiting for connections...
Received connection request
Received input: Look Ma...all backwards
Sent output: sdrawkcab lla...aM kooL
Received input: jack frost
Sent output: tsorf kcaj
Received input: END
Socket terminated

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