PHP fgets返回空字符串[关闭]

Question

I want to make telnet connection to a server and send commands to that. I successfully made the connection and sent the commands, but when I want to read the results with fgets, it's returning empty strings.

$socket=fsockopen($host, 25, $errno, $errstr);
if ($socket!==false){
    fputs($socket, "helo hi
");
    fputs($socket, "quit
");
}
fclose($socket);
$buffer=array();
while (!feof($socket)){
    $buffer[]=fgets($socket);
}

This code returns empty strings with fgets and does't stept the file pointer in the stream output. What is the problem with that?

Answer 1

You close your connection before trying to read what your socket returns.

Imagine the following: You can't remember anything until you're explicitely told to do so.
Do the following brain game: Open a file. Now write something in it. Then close it. And now tell me the content of said file. You would also tell me you don't know, because you didn't read what was in it. You closed it before reading what is in it and therefore don't know what is written in it.

What do we learn from that? We need to read the socket before we close it.

$socket = fsockopen($host, 25, $errno, $errstr);
if($socket !== false) {
    fputs($socket, "helo hi
");
    fputs($socket, "quit
");
}

$buffer = array();
while(!feof($socket)) {
    $buffer[] = fgets($socket);
}
fclose($socket);