PHP socket not working properly

Question

I have established a server to listen to incoming requests through port 1122 on my 127.0.0.1 Here is my code :

<?php

// set some variables
$host = "127.0.0.1";
$port = 1122;


// don't timeout!
//Since this is a server, it's also a good idea to use the set_time_limit() 
//function to ensure that PHP doesn't time out and die() while waiting for 
//incoming client connections.

set_time_limit(0);


// create socket
// The AF_INET parameter specifies the domain, while the SOCK_STREAM 
// parameter tells the function what type of socket 
// to create (in this case, TCP).
//If you wanted to create a UDP socket, you could use the 
//following line of code instead:socket_create(AF_INET, SOCK_DGRAM, 0)

$socket = socket_create(AF_INET, SOCK_STREAM, 0) or die("Could not create
socket\n");


// bind socket to port
//Once a socket handle has been created, the next step is to attach, 
//or "bind", it to the specified address and port. 
//This is accomplished via the socket_bind() function.

$result = socket_bind($socket, $host, $port) or die("Could not bind to
socket\n");


// start listening for connections
//With the socket created and bound to a port, it's time to start listening 
//for incoming connections. PHP allows you to set the socket up as a listener 
//via its socket_listen() function, which also allows you to specify the number 
//of queued connections to allow as a second parameter (here 3)

$result = socket_listen($socket, 3) or die("Could not set up socket
listener\n");


// accept incoming connections
// spawn another socket to handle communication
//Once a client connection is received, the socket_accept() function springs 
//into action, accepting the connection request and spawning another 
//child socket to handle messaging between the client and the server.
//This child socket will now be used for all subsequent communication 
//between the client and server.

$spawn = socket_accept($socket) or die("Could not accept incoming
connection\n");

// read client input
//With a connection established, the server now waits for the client 
//to send it some input - this input is read via the socket_read() function, 
//and assigned to the PHP variable $input.
//The second parameter to socket_read() specifies the number of bytes of input to read - 
//you can use this to limit the size of the data stream read from the client.
//Note that the socket_read() function continues to read data from the client 
//until it encounters a carriage return (\n), a tab (\t) or a \0 character. 
//This character as treated as the end-of-input character, and triggers 
//the next line of the PHP script.

$input = socket_read($spawn, 1024) or die("Could not read input\n");

// clean up input string
//The server now must now process the data sent by the client - in this example, 
//this processing merely involves reversing the input string 
//and sending it back to the client. 
//This is accomplished via the socket_write() function, which makes it possible 
//to send a data stream back to the client via the communication socket.
//The socket_write() function needs three parameters: a reference to the socket, 
//the string to be written to it, and the number of bytes to be written.

$input = trim($input);

// reverse client input and send back
$output = strrev($input) . "\n";
socket_write($spawn, $output, strlen ($output)) or die("Could not write
output\n");


// close sockets
//Once the output has been sent back to the client, both generated sockets 
//are terminated via the socket_close() function.

socket_close($spawn);
socket_close($socket);
?>

this will listen to the client and return a reversed value of the inout.

The code will not give any errors. in fact when I go to localhost/socket.php it will keep loading.

Now I open a telnet connection using terraterm and a white page appears, If I input any value or strike any key the connection will be lost.

Any idea why this is happening ?

Kind Regards

Answer 1

The problem is probably that your tera term is using the "character mode" which means that every character typed is directly send to the server.

This causes the socket_read to immediately return with just one character read.

You could set the PHP_NORMAL_READ when calling socket_read:

$input = socket_read($spawn, 1024, PHP_NORMAL_READ)
    or die("Could not read input\n");

Without that flag socket_read does not read until a \n is written.

Otherwise it behaves normally. The script doesn't write any output to the browser so the browser just waits until some timeout sets in (your Webserver might terminate the PHP-script because nothing is written).