Sockets: is there a way to check if the remote host didn't close the connection?

host,port,connectiontimeout,username,password are pre DEFINEd values

function connect() {

$sock = @fsockopen (host, port, $errno, $errstr, connectiontimeout);


if ( $sock ) {

fputs($sock, username."\n");

fputs($sock, password."\n");

}


return $sock;

}



after sending the username and password, server will check if these values
are correct, if not, it'll disconnect the connection

Is there a way to determine if the connection still exists after I'm sending
the username and the password?

thanks!