sudo iptables -A FORWARD --port 10 -j ACCEPT

iptables v1.4.4: unknown option `--port'
Try `iptables -h' or 'iptables --help' for more information.

sudo iptables -A INPUT -p tcp -d 0/0 -s 0/0 --dport 10 -j ACCEPT

Chain INPUT (policy ACCEPT)
target     prot opt source               destination         
ACCEPT     tcp  --  anywhere             anywhere            tcp dpt:10 

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination 

Starting Nmap 5.00 ( http://nmap.org ) at 2010-07-28 20:43 WIT
Warning: Hostname localhost resolves to 2 IPs. Using 127.0.0.1.
Interesting ports on localhost (127.0.0.1):
PORT   STATE  SERVICE
10/tcp closed unknown

Nmap done: 1 IP address (1 host up) scanned in 0.23 seconds

// set some variables
$host = "localhost";
$port = 10;
// don't timeout!
set_time_limit(0);
// 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");
// accept incoming connections
// spawn another socket to handle communication
$spawn = socket_accept($socket) or die("Could not accept incoming connection\n");
// read client input
$input = socket_read($spawn, 1024) or die("Could not read input\n");
// clean up input string
$input = trim($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
socket_close($spawn);
socket_close($socket); 

Starting Nmap 5.00 ( http://nmap.org ) at 2010-08-01 23:48 WIT
Warning: Hostname localhost resolves to 2 IPs. Using 127.0.0.1.
Interesting ports on localhost (127.0.0.1):
PORT   STATE SERVICE
10/tcp open  unknown

Nmap done: 1 IP address (1 host up) scanned in 0.08 seconds

iptables -F
iptables -X
iptables -t nat -F
iptables -t nat -X
iptables -t mangle -F
iptables -t mangle -X
iptables -A INPUT -p tcp --dport 10 -j ACCEPT

/etc/init.d/iptables save

/etc/init.d/iptables restart

sudo iptables -A INPUT -p tcp --dport 25 -j DROP

echo "1" > /proc/sys/net/ipv4/ip_forward
sudo iptables -t nat -A PREROUTING -p tcp --dport 25 -j REDIRECT --to-ports 5000

sudo iptables -A INPUT -p tcp -m multiport --dport 22,222,2222 -j ACCEPT

Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

Starting Nmap 5.00 ( http://nmap.org ) at 2010-08-02 01:31 WIT
Warning: Hostname localhost resolves to 2 IPs. Using 127.0.0.1.
Interesting ports on localhost (127.0.0.1):
Not shown: 100 closed ports
PORT   STATE SERVICE
80/tcp open  http

Nmap done: 1 IP address (1 host up) scanned in 0.18 seconds

sudo iptables -A INPUT -p tcp --dport 80 -j DROP

Chain INPUT (policy ACCEPT)
target     prot opt source               destination         
DROP       tcp  --  anywhere             anywhere            tcp dpt:www 

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination 

Starting Nmap 5.00 ( http://nmap.org ) at 2010-08-02 01:38 WIT
Warning: Hostname localhost resolves to 2 IPs. Using 127.0.0.1.
Interesting ports on localhost (127.0.0.1):
Not shown: 100 closed ports
PORT   STATE    SERVICE
80/tcp filtered http

Nmap done: 1 IP address (1 host up) scanned in 2.55 seconds