I need to scan the open ports of my server.
I tried nmap by: `nmap ***.dyndns.info` from within my local network.
It gave me:

```
Starting Nmap 5.21 ( http://nmap.org ) at 2011-04-09 16:05 JST
Nmap scan report for ***.dyndns.info (***.***.***.39)
Host is up (0.00097s latency).
rDNS record for ***.***.***.39: ************.ne.jp

Not shown: 994 closed ports
PORT      STATE    SERVICE
23/tcp    open     telnet
53/tcp    open     domain
80/tcp    open     http

```

Then I tried the open ports tool provided by dyndns.com by specifying a specific port like:

```
global ip address 23
global ip address 53
global ip address 80

```

For each of those tests, it gave me "timed out" as a result, which is contradictory with the nmap results.

I know that depending on the way that nmap performs the tests, it may turn out that the result is "open".

So, I think the best way to test the ports of a given server is from outside, like the dyndns open ports tool.
But I'd like to test all ports at once, as opposed to one by one.

Is there any reliable tool for that, especially that I can use in command line?
I am on ubuntu 10.10.