PHP socket server answer eof char to linux telnet

I want to talk with php server with socket by telnet.

I wrote 'echo' server (i send string to server, server send it to me)

i use chr(0) on end of output string to send information that string is sent

socket_write($client, $output.chr(0));

but telnet haven't see it and i cant send new string

TELNET

telnet 127.0.0.1 9000
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
hello
hello_

PHP

<?php
set_time_limit (0);
$address = '127.0.0.1';
$port = 9000;
$sock = socket_create(AF_INET, SOCK_STREAM, 0);
socket_bind($sock, $address, $port) or die('Could not bind'开发者_运维百科);
socket_listen($sock);
while(true) {
    $client = socket_accept($sock);
    $input = trim(socket_read($client, 1024));
    if ($input == 'off') break;
    $output = $input.chr(0);
    socket_write($client, $output);

}
socket_close($client);  
socket_close($sock);
?> 

what i'm doing wrong?

You should end the lines with carriage return or "\r\n", instead of just the \0 character. The telnet client watches out for them too I think.

The real problem however is your use of $client = socket_accept(..) within the loop. You must only establish the connection once, before the while. Otherwise you will reset the connected stream.